Peace Rockbrother... Remember the Oath.
LOL! But yeah, Sandgorgon's Doom was kind of good and bad. I mean, it was good for the Bhrathair because it finally gave them a chance to live in peace and work toward creating life in the desert. But at the same time, I believe it was as Linden guessed... that the Sandgorgons weren't so much a destructive force; they just destroyed whatever came between them and whatever their obscure goals were. Nom somewhat proved that the Sandgorgons could think and reason by listening to what Covenant said and actually bowing to him in thanks for his freedom. Of course, Covenant had to beat him down first, but I know some people that are just as stubborn so we won't go that route.
Also, the Sandgorgons destroyed each other in their frenzy to try and escape the Doom. Their numbers dwindled each year. The Lords and the people from the past eras of the Land would never have imprisoned a race of creatures in such a way, not even such evil creatures as the Cavewights or the ur-Viles. It violates the Oath of Peace with its very nature, and therefore, to me, is corrupt. So once again, it's a matter of perspective, to be argued either way.
But it is a fitting way to point out that perhaps in all the Earth there is no Lore which could effectively be used without violating the Oath of Peace. Earthpower itself has the power to be a destructive force, so why should humans be any different?
Those babies killed 200 Giants, after all!!! 
