I thought you'd be as opposed to the idea as I am.
I'll be the first to admit, the chances of me beating you in a debate, even with you arguing a position that you normally disagree with, is pretty much nil. In fact, that would probably be true even if I were actually arguing at full strength for a view I did agree with. You're way smarter than I am.
However, on the off chance someone thinks my arguments are better than yours, I don't want to argue for a position that isn't mine, because I have an issue with trying to persuade people of something I myself don't agree with. What if I succeeded? I'd actually feel bad about myself. I wouldn't WANT to succeed in that environment. I'd actually WANT to lose and thus hopefully get people to switch to the position I DO support.
I couldn't do it