I'm sure some do.
Others will use such jokes because they know it gets on people's tits.
I've literally lived with gay people. Someone very important in my life, when I first left home, was a closet gay and is now openly gay. I've seen plenty of people go through that difficult situation.
If someone called me gay I'd tell them that I'm not. It doesn't bother me. I don't see being gay as being bad.
But I know people do. So I use it because it gets to them.
But if you want to think everyone's homophobic, I'm fine with that too. Doesn't bother me, your life, your anger. I have my own anger to deal with and it's got fuck all to do with sex.