Alyssa Rosenberg responds to people mocking Marcus Bachmann's lisp and implying that he's gay:
One of the funnier inversions of this trope I’ve seen was in Friends With Money where everyone assumed Frances McDormand’s husband was gay even though he wasn’t. Turning stereotypes back on the people who hold them is almost universally funny than confirming them. Things like this won’t win the battle against Rep. Michele Bachmann as a viable national political figure and help delay victory in the larger war over gay rights.
Here's the other problem with aiming gay jokes at presumably closeted homophobes: It reaffirms the idea that being gay is funny. If the objective is defeating homophobia, it hardly helps to tell jokes that homophobes can guffaw along with. They're thus reaffirmed in their belief that there's nothing wrong with mocking gay people for supposedly being "effeminate," since, after all, even gay folks think "those people" are hilarious. Ultimately gay people, rather than people who hate gay people, are the butt of the joke.