I'm sure his answer would be something about trying to jettison the effects of you brainwashing me.
The real answer, however, has nothing to do with being brainwashed and everything to do with being right. He knows he is wrong. He can just never confess that to himself or anyone else because he can't stand to live outside of his delusions of being right. Therefore, you just keep hitting him with reality checks. Each time you do that, he has to try just a little bit harder to keep his delusion from crashing down around him.
And, of course, him scrambling to keep his delusions from crashing around him is what creates comedic gold.
