Originally Posted by
ravenmoon
They can. Because blizzard built the story of them getting involved with the void out of a motivation to save and defend. Save Azeroth, defend Silvermoon, and not give in to evil.
The reason they do the void is because they can wield it without becoming evil and growing insane. "Magister Umbric: We can harness this power for good" - whiles a lot of people may not understand, because the void is evil and dangerous, however those who can wield it without giving into the whispers are not necessarily evil. It's when you give in to the whispers you go insane and start carrying out the evil will of the void.
The whole point of voidv elves and Alleria is that you do not do this, they are the first to successfully resist its whispers and thus wield its incredible power. And the ones you follow and train as/with, they are definitely good. How do I know this? Because they state their intention, as does Alleria who has proved that despite wielding the void she is not evil nor immoral.
I'm sure you can role play an evil void user, you can be evil and not insane, not controlled by or given in to the void, that's a personal issue. But the ren'dorei are not evil as a group, nor iummoral.
They've explained the whole situaiton about the void enough for you to grasp that the void is bad because of those that drive you to insanity, however the few gifted enough to wield it without succumbing to it, well, they're not bad at least not yet.