Even on shows like Saturday Night Live the normally leftist comics would get the hiss treatment if they ever did bits with gay characters that were anything but celebratory.
I believe Norm MacDonald lost his job because of one joke against Magic Johnson and one against Michael Jackson that could be taken as anti-gay by humorless idiots with thin skins.
My feeling is that the audiences were stacked by organized groups of gay advocates. There were a number of comics that were still doing bits that were meant to offend everyone like Dice Clay, etc. I think the gays decided they had enough of that and decided to hiss everyone off stage who didn't stick to the program.
I can remember the look of complete surprise on the faces of some of the comics when they were doing stuff that must have killed in the clubs, but was met with a barrage of hissing when they finally got their first TV appearances.
This "jamming" has been going on for some time IMHO.