Maybe you have a deontological soft-spot for gays, or you have an egoistic preference for the wellbeing of gays.

Not for gays specifically, of course, just for all minorities who share the "born that way but can be broken into a different mold by torture+brainwashing" pattern. If Mormons tried those "shaming" tactics, etc on, say, opponents of transhumanism or borderline-autistic geeks, I'd speak out for those. Because I feel that, socially, manipulating people like that is a line that should not be crossed.

Well, of course I take it personally being bisexual myself, but still - I spoke out for gay rights even before I realized my own sexuality, just because it always looked like a glaring injustice to me.