Of course, the commenters respond to his question by denying that they've been sexist. They're good little commenters, so they don't want to be something bad, and they accept that the thing that sounds bad — sexism — is bad, and therefore no one can say anything interesting.
But obviously, the human mammal has a response to the perceived sex of another human mammal. All sorts of conscious and unconscious thoughts and feelings flow through the nervous system. It is the most interesting topic of conversation. Don't squelch it! Facilitate it!
Why have diavlogs at all if not to expose the physicality of the interlocutors? If you want to exclude reactions of the more complex emotional/sexual kind, then let's stick to writing... and use sex-neutral pen names. If we're going to appear and speak out loud, we're doing something that has an elaborate effect on other human beings, and that's not something to deny and pretend not to see. It's something to observe, have deep (and shallow) thoughts about, and analyze — seriously and jokingly — in writing and in speech.
We're so afraid of hurting other people and of being thought ill of that we make ourselves into crushing bores.
Bonus: Here's an August 2008 BHtv segment in which I talked with Megan McArdle about why female diavloggers inspire wrath.
AND: Here's the BHtv link to see the kind of answers Bob got to his question.