There are very few portrayals of us in the media that are not offensive to me. I could count them on my fingers. Even ones that are genuinely funny, like on Frasier, where Roz predicts a drag queen will wind up with her bridesmaid dress; still offend me in the way they play off bad stereotypes and outdated idioms.
But one episode of Family Guy included one of the good ones. The episode where the wife doesn't realize her new female friend is a drag queen who lives as a woman. So I cut the show some slack on the latest episode. The dog barfs entirely too long, which is insulting, even though it made me laugh both times I watched it. And she boinked a dog, and it made the dog barf. That's pretty insulting.
However, the ignorant things the family says, which are hopefully exposed to the audience as ignorant; I think that's affirming. It helps smart and sensitive people understand what we are up against.
In conclusion, I don't wish the episode didn't exist or didn't air; but it's a close call.