When Chris first started identifying as a tomgirl crossdresser intersex whatever, his original definition covered "LBT Pride", specifically excluding gays but not bisexuals. Bob probably told Chris that gays are bad, including bisexuals in that definition because he was old as fuck and didn't know or care about the difference. Then Chris wouldn't have developed the same kind of disdain for bisexual people because he's autistic and takes things exactly as they're phrased to him. "Homosexuality is bad according to my father, who is wise, but he didn't say anything about this other similar thing, so it must not be as bad."
It would be interesting to know if he would take issue with two bisexual men being in a relationship; if they're not calling it "gay", would Chris be okay with it?