Especially when its your boyfriend or someone you have an interest in?
Most Helpful Girl
Yes, I would be offended by that, just as I'd be offended by sexist or racist jokes. The 'it's a joke' excuse just doesn't wash: those comments show an ignorant and bigoted attitude that stereotypes and degrades people. And that's just not attractive in the slightest.
Plus, how do you know that the girl you like doesn't have a gay relative? You could be making a joke against a favourite uncle, or a brother.