It's funny; I don't even remember the big to-do about it that you're describing. I don't even remember it period.
I'll tell you what, though. If there was a large group of liberals going after him, the way the birthers are going after Obama, I wouldn't defend them, like you're defending & legitimizing the birthers; I'd be embarassed for them, for undermining the more legit case that people were trying to make against McCain's politics.
I've always been that way. I was embarassed by things like Rathergate & other efforts to tear down those I didn't agree with that didn't focus on the specific policies I disagreed with, and were more interested in just bringing a man down. To me, those efforts belittled & distracted from the real issues, what what should really be debated.
Clearly, your priorities are different, though.