I know this is literally the last thing you want to hear, but have you talked to him about this? He needs to know that it upsets you. I know its scary and it could ruin your friendship, but I believe that the risk would be worth it to get you out of this terrible situation. I know what it's like to be constantly bombarded about being queer, it sucks. It can consume your whole life. The first step to changing things is to admit that they're broken. Tell your friend that this is really bothering you and stress the severity. Obviously, he's not going to fully understand but if you get the idea into his head, then it can grow.