Tell them what you just told me: that their homophobic jokes are gross.
If they pull the “But it’s just a JOKE!!!” routine, remind them that offensive jokes are still offensive and are contributing to the problem of homophobia by equating gayness with badness.
It’s like people who use “faggot” to insult people. They usually say that they don’t mean it to mean “gay,” but the fact is, it DOES mean “gay” in a lot of places, and so it’s still contributing to the problem of homophobia.
If they still won’t stop, tell them firmly that you don’t like their homophobic “jokes” and they need to stop or you’re not going to want to be around them anymore. If they’re meant to be your friends, they’ll respect that. If not, they won’t, and that’s good, because who the hell wants to be friends with homophobes, “joking” or not?