That's irrelevant though. What a person finds offensive doesn't need to be based in reason. These people have been indoctrinated into hating gays, so the way they feel is comparable to one's hatred of pedophiles. (Also, I'm assuming pedophile in this context is the same as child molester).
Heterosexual is not rhetorically equivalent since heterosexuals are not viewed as evil by 40% of the US population. If it makes you feel better, a more equivalent comparison would be polyamorous or incestuous characters, although I do not know if you personally would find that distasteful.