And there are plenty of other reasons to discuss this sorta thing. Maybe your personal faith is fine, but if you think (as plenty of christians do) that christ is THE only salvation for humanity, then it's reasonable in my view that a christian would be agressive in trying to defend their faith. From their POV someone's soul is in the balance every time they get in such an argument - perhaps this person, too, can be saved. So while I have found it rather tiresome on the one instance an evangelical christian has tried to convert me, I see where people like that come from.I can actually agree with this statement to an extent. There does seem to be, however, an insinuation that pointing out bias against Christianity equals taking criticism to heart. I assure you, attitudes on these forums do not touch my personal faith. If you saw self-satisfied Christians sneering at ignorant and backwards agnostics and congratulating each other on their cleverness you might feel peeved without feeling your conviction of the correctness of agnosticism (or pantheism or whatever) threatened and might even want to express how you feel.
And it's not like people who are fully comfortable with their beliefs should never defend them.