Redskinluver:
Its the evangelical,fundamentalist Protestants, those who are rightwing in politics, Trump supporters, and anti-science, who are most vocal homophobes.
Those are also the supposed 'Christians' who are by far the most likely to support domestic discipline, albeit of course only of the husband-spanks-wife variety, and also ironically to condemn any marital spanking situation if it's engaged in for kinky erotic pleasure. (However, I'm figuring that many evangelical 'Christians' involved in spousal M/F DD are gratified sexually by it, although they won't ever consciously admit to feeling like that.)
You're correct in stating that they'd be even more repulsed by F/F or M/M spanking, especially within a marital/romantic relationship, than they would by any wife-spanks-husband domestic discipline, since after all these 'Christians' totally reject gay marriage and highly disapprove of gay eroticism.
Evangelical 'Christianity' in the U.S.A. today has unfortunately become an authoritarian political movement, its religious trappings designed primarily to control people's voting behavior...

--C.K.