There's a lot of groupthink going around. I don't think it's the same as brainwashing, it's just that people -- and, it is worth remembering before you crow about how right you are, people from all parts of the political spectrum -- tend to crowd together with those that agree with them.
The problem I have with the "brainwashing" attack is that it's just irrefutable. I can't claim not to have been brainwashed as soon as I'm accused of it because, well, that's exactly what a brainwashed person would say, isn't it? At the same time, I think there's a certain irony in the idea that anyone who disagrees with you is automatically brainwashed, ie incapable of free thought, which itself closes you off from the possibility that you are wrong.
But anyway. The accusation of brainwashing is unfounded, even with this anecdote. And besides, it ignores -- once again! -- the importance of what goes on at home.