Enjoy most: the prospect of having an impact on the public debate. Irritating liberals is a close second.
I'd pretty much debate anybody. I prefer to debate smart liberals. I'm not saying this about Stephen Colbert but, unfortunately, the most famous liberals generally aren't the smartest ones. I have a list of the smarter liberals I recommend.
Obviously, I'm a fan of satire. I'd debate anyone, but it would have to be the actual person. That would be my only hesitation about debating Stephen Colbert. If he were playing a character, it wouldn't really work.