heteroactivist

A person, usually with schizophrenia, who wrongfully believes LGBTQ+ people are trying to turn him and the population gay. These people tend to want to be gay but they are in denial and are trying to justify their perceived straightness.

Matt W.: "I'm not homophobic, I'm just a heteroactivist."
Joe B.: "Dude, we all know you're gay, just accept it."