I'm late on this, I know, but I'm trying to figure out what the hell Dana Milbank was thinking. With few exceptions, the "bitch joke" is the marker of a male mind confronting its own limits and a formidable woman, at the same time. It is the fuel gauge on the dashboard sagging past "E."
I won't attempt to separate the sexist from the stupid, here. They may well be one in the same. But I imagine it must be grating to be lectured to on what is/isn't sexism from a beneficiary. That said, I will offer this--when a man starts reaching for the bitch jokes, you've probably won.
UPDATE: Let it go boys. A HuffPo commenter nailed it--"The trick is to stop digging."