I am the Devil's Advocate

I argue evildoers to death. They cannot win because I don't really have a position. Just when their minds begin to crack I tell them that I agreed with them all along, and that's all it takes to turn them into sniveling piles of impotence. I moonlight as an old guy who trolls forums on the internet, mediating arguments and making everyone feel like they're right. So I'm a good troll. My costume would be a black & white suit.
My arch-enemy would be Grayman.