Livre d'Or

But there's probably a reason for it to do with strengthening the Spiritual domain, because a church than control its members' sexuality has a very major emotional hold on them.

Religions which have a cost to following them (not necessarily monetary) do better than those which don't make demands on their followers, ISTR (I'd like to be able to quote the research here but I can't think of good search terms). This is a bit like what someone said in the locked discussion that a liberal religion didn't seem worth getting out of bed for, I suppose.

I'm not sure what the psychology of that is. Maybe it's a bit like when you never buy the cheapest brand, or maybe people want challenges and want to be part of a narrative where they struggle and perhaps overcome them. Back when I was an evangelical Christian, a common piece of jargon was to say "I was challenged" (by that sermon, say) to mean that "I've realised I'm falling short there".

Why specifically homophobia? Well, it's the patriarchy, innit? Also, if you're going to pick an out-group to strengthen your in-group by having an identified enemy, it's good to pick a sin to which few of them are tempted.