As the transcript at Media Matters indicates, Hitchens told Sullivan (who is gay), "Don't be such a lesbian. Get on with it."
Sullivan doesn't exactly look put out by his friend's comment, and later responds on his blog to the criticism of Hitchens, "Some people really need to get a sense of humor."
A commenter at Ann Althouse's blog claims,
Hitchens has a gay sensibility and that is a term that some gays say to others at times when they act like Sullivan was acting in that clip.
Obviously, lesbians are heavy on the foreplay, oils...baths...whereas a good gay man (titus?) has fast dirty sex and gets it over with. Hitch was just asking him to "hurry it up" with his point.
Since I don't have the required "gay sensibility" (Dave in SF will even vouch for my dislike of Andrew Lloyd Weber), I cannot say one way or the other, except to note that Sullivan obviously got the joke whatever its point or comedic value.
Of course, I doubt Media Matters would have even noticed Hitchens' joke if Hitchens didn't talk about Hillary Clinton later in the same interview:
"I just think that if she knew how it made her look, sort of alternately soppy and bitchy, she'd stop it. But she can't help herself, can she? She just can't."
Is that Hitchens' way of saying Hillary Clinton should stop behaving like a gay caricature?
