He is not going to sell a significantly greater number of albums just because he was there. Most of us were definitely not his target audience, and his name is already fucking everywhere. The name that's getting spread further is Invisible Children, which would be the volunteers doing more work. Also, after listening to his speech, he was totally sincere about it. It would be different if it seemed like he was just there to join in on the publicity, but he definitely came off more as if he was there to share his publicity with Invisible Children and the people up in Northern Uganda. (read: he cares about this)
Besides, what kind of fucked up person looks at children being forced into the army, forced to kill friends and family from their village at a young age, and mutilated as punishment(ears, lips, nose cut off), and then thinks "I can totally cash in on this, make a profit." It's not really much of a moral grey area here, Joseph Kony's pretty fucking out there, and he needs to be stopped.
but whatever, the point is, he is human, even if he's in a shitty band, and there's no point on judging him differently just because he's famous. Get the full story, then decide whether or not you think he sincerely cares for the cause, then judge him.