Pretty messed up. I have a sort of related story. My friend grew up in Venezuela, in a traditional, religious family. He has some pretty weird views about homosexuality. He believes it to be a choice. He believes gays just choose to be attracted to the same sex. He thinks its become a cool new thing to say to get attention. I know, its weird. Any of you have similar stories? how did you approach it? We talked about it here and there, but I just don't bring it up anymore.
If you do want to talk about it or if it comes up, I would ask him, very calmly, for his evidence. "How do you know that?" "What's your evidence?" and then bombard him with online studies that show the opposite.
If he says, "It's against nature." Show him evidence of homoerotic behaviour among other species.
If discussing it makes you afraid you will be accused of being gay, there are things to say in response to that.
Most people probably just find new friends in cases like yours. Good luck.