Kant does not present reason as an enemy of faith. As for finding disagreement between Kant and the Lewis chapter, most of which I read yesterday, it is difficult because they do not always discuss the same topics, and because Lewis does not mention Kant directly.
Here is a webpage which I googled up discussing a common Kant topic in the context of Lewis's article "The Weight of Glory."
www.dennyburk.com/?p=501
It is common to see a denial of Kant based on the concept of desire when in fact Kant explicitly appealed to Desire. And moreover, it is common for critics to take on Kant without apparently having read the works as is obvious with Lewis since the Kantian concept of Desire is crucial to understanding practical reason.
And so if your understanding of Kant comes through Lewis, it is now apparent why it is that every time you make a claim about Kant the exact opposite of your claim turns out to be the reality.
Of course when I turn to NewAdvent.org for information about Kant, the very same thing happens. All I have to do is follow the inverse of the teachings at that site in order to derive the facts of the matter.
Sorry you have trouble with my 'pejorative' term "groupthink." It is based on nothing more than the unwillingness of individuals within a group to go against the will of the majority. Of course there will be the heretics, but groupthink usually wins the day. But I'm glad that my 'ripples in the pond' analogy was more pleasing to you.
More striking with Orthodoxy, however, is the authoritarianism prevalent with it. This goes against my very nature, I don't need Kant to defend me from it, I was already born that way. I am an innate heretic.
I looked up "Orthodoxy" on the Princeton site just to make sure, and came up with "a belief or orientation agreeing with conventional standards." But who defines conventional standards or wisdom? The sacred texts. And on what grounds? On a human interpretation of their meaning. And who gets to decide this? The Church, which primarily consists of a group of priests. What happens to those who disagree with the will of the group? They are cast out and declared heretics. Since almost nobody wants to be punished this way, what is the result? Groupthink.
I stated that common sense varies from culture to culture in order to contrast it with a more cosmopolitan "universal sense" common to all humankind.
However, you define common sense as that which senses Truth, so I don't see how we're even on the same playing-field here. I don't think you'll find a general definition of 'common-sense' that states anything about sensing Truth.
I don't see where you think Kant assumed that "man is an animal," or to say it better, "only an animal." In this it is important to consider Kant's upbringing as a strict Lutheran Pietist and how this affected his later philosophy.
We diverge sharply on the Orthodox point you make about the will killing the soul, leaving only the animal. For Kant, the will is always good, at least in intention if not objectively. I don't know what it means to kill the soul, but the will itself can be deadened by previous choices which eventually render all power of choice more difficult. We choose our habits, and thereafter, habit chooses us until there is a "change of heart" or a "revelation" experience. And both these latter ideas are contained in Kant's work on religion.
Kant is more concerned with furthering the will's ability to make good choices than with notions governing the soul which are cast into the noumenal realm. And I think this boils down to criticizing religion's view on heaven and hell, although he doesn't explicitly state it - for one reason, Kant was not fond of the idea of being thrown in prison for his beliefs, and in that day and age it was a real possibility. Kant did not believe that the threat of punishments was good for developing a good will. He would not think that developing a good will was justifiable through such ideas as soul-death. He did not think that people could be scared into doing the good. And indeed, a human robot-like figure who always does the good automatically is not good at all. The good is not even the result of being born with a propensity toward doing good, as with a human born with a philanthropic nature. He may do good works, but they are not the result of a good will but only an inclination to doing good.
The good will manifests itself in a resistance to doing evil. So the Fall from Grace is an integral element of his moral theory. Man, in order to do good, must be able to contrast it with the fact that he is 'warped wood' with a propensity, not toward the good, but toward evil. It is only good, therefore, when contrasted with evil or with inclination in general which is not a product of the good will. The good will is strengthened against this inherent or innate propensity toward evil through making good moral choices, that is, choices in line with the categorical imperative.
The categorical imperative is not Kant's variation on a sacred text, as many have claimed; it is however his own distillation of what he sees as the moral tendencies in people, so it is based in reason and anthropological observation and not on sacred texts. Thus Kant stated that he did not bring a new set of morals at all, only a new formula for deciding what is to be moral.
This formula, of course, is based on reason and not faith.
However, if you were to say that Kant held reason as supreme, I would have to know what you mean by that. Kant was not decided concerning this or that faculty's supremacy or magistry, only on how it affects the whole. So there is also ample room for faith in his philosophy, and he is infamously known for saying that reason must at need be denied in order to make room for faith. Faith provides an opening for the good will to grow into, otherwise it would be stifled by many empirical ponderings such as were mentioned by Lewis in that book you cited. There would be no hope without faith, hope is essential to understanding Kant's moral views. But so often people, perhaps such as yourself, confuse all 'reasoning' with 'empirical reasoning'. And so you are led to Lewis's critique of empirical reasoning as deadening hope and furthering the idea that existence is futile. But that is not Kantian reasoning which explicitly makes room for the concepts of hope and faith.
Continuing on with your post, I do not equate authority with guidance if authority is seen as authoritarianism which stifles the will of the adherent. Doing good works under blind allegiance to an authority's will is not proper to morality. Guidance is a separate issue altogether. Some would proclaim that Kant is obviously writing as a kind of authority on moral issues. However, when he states that someone could come up with a moral basis other than his notion of the good will, when he says that this basis is only provisionally postulated, and that another basis may be possible, one could hardly deem that authoritarian or dogmatic. It would be like the Church claiming that the doctrine of Propitiation is only provisionally valid until someone happens to come up with another doctrine. It just doesn't happen. And so it is on this basis that I separate dogmatic faith from Kant's rational faith, and this is where Kant and the Church part ways forever.
For Kant, it could be said that reason reigns supreme in general only in the sense that reason is fallible. Fallibility makes dogmatism impossible, and faith is dogmatically inclined toward the infallible. For all your faith in the sacred texts as infallible, even granting you their infallibility, they are yet based on a human interpretation of their meaning. Thus the meaning of the sacred texts is prone to fallibility even if not the texts themselves. So you can have faith in them all you will, but the basis for your religious existence is not the texts themselves but a human interpretation of their meaning for you. Whether or not this interpretation is humane - contrasting with the inhuman extremist Muslim interpretations of the Koran - depends not on the texts themselves, whatever their true meaning is, but on how well your reason is informed by the will which is good and by the CI. And so the good will, in the moral context, reigns supreme over reason. The final end of the good will Kant termed the Holy Will which is complete individual moral perfection, or to put it in more Kantian terms, the complete satisfaction of reason in all its practical, moral ends.
It is only because King Frederick of Prussia eventually died in 1786 that Kant was able to write this at all without being imprisoned for it. That tells me a lot about faith-bound hope. The Church, Catholic or Protestant, has a bad rep for basing punishments on a lack of proper obedience to Earthly religious authority. It is only because we in this country live under a rational Constitution that the Church's capacity for such evils has been stymied. And it is only because of Enlightenment thinkers such as Kant that such freedom from the strict bounds of elite religious authority is possible at all.
Yet I think you're taking my term "elitism" too far. It is intended only in the sense that some group has a monopoly on religious truth that you can't possibly understand (faith over reason), therefore your only hope is through blind allegiance to the doctrine. Or let's say, their reason is better informed by God or holy wisdom, and so your only hope is through blind, irrational sheep-like faith. This elitist attitude was more obvious before Luther nailed his 95 Theses on the church door and started the Protestant Reformation, at a time when nobody outside the priesthood was allowed to own Bibles. This is pretty much the same attitude in the Church today, where anybody can own a Bible but nobody in the congregation is taught the meaning of its Word or encouraged to read it on their own. Truth, instead, is to be found through adherence to sacred rituals. And so in this way, people are controlled through inculcating ignorance as a sort of "original intellectual sin," and by being taught that relying on their own rationality is futile.
As for your last paragraph, Kant is famous for stating that man is "warped wood" and that he has an innate propensity for evil. He completely agrees with Church doctrine on this. However, the way out for Kant is not through the propitiation of a heavenly savior but through the establishment of a rational constitution here on Earth. So while his goals are informed, in a way, by ideals not of this Earth such as the Holy Will, the goals themselves never find their way beyond it.