Image via WikipediaLet's say that the Pope, the Cardinals and Bishops, and the rest of the hierarchy of the Roman Catholic Church decided that women should be priests, priests can marry, that homosexual acts aren't disordered, etc, etc. Or that the most conservative members of the Anglican Communion drop their objections to ordaining unapologetic homosexuals. The big changes that progressive Christians tend to talk about. This is not about inviting people to explain why this cannot happen because of tradition or church law - it's just a hypothetical, a thought-experiment.
Then those fighting for such change become the traditionalists, don't they? Once they have things just as they believe they should be, how would they react to radical change? What if other groups were lobbying to have acceptance for bestiality, necrophilia, etc? I am not drawing a direct moral equivalence here, but a relative one. That is, while some may not have a problem with homosexuality, bisexuality, etc, they likely have a problem with these other practices. Referring to performing such acts as "disordered" may even be perceived as an understatement.
So how would we want the Church to respond to people who had for whatever reason developed a sexual interest in animals or corpses?
It is a mistake to see homosexuality/bisexuality strictly as sexual preferences or as sex acts - it also involves forming close, intimate relationships with people of the same sex. This again isn't in dispute. But seriously - how might we respond with charity (caritas, agape) to people who had the compulsion to fulfill urges we might find disordered? Might we not attempt to encourage them to abstain from this behavior? How might we phrase our concern for the person and couple with it concern for the consequences of their actions? How would we want to express it without compromise but without condescension?
Yes, we have our reasons for how we would move the line of acceptability - our arguments separating and distinguishing sexual orientation, sexual fetishes, sexual addictions, sexual disorders, etc. There are arguments for the traditional drawing of the line. There are arguments for drawing the lines far beyond what many of us would find remotely comfortable. However the line does or doesn't move, our first and primary concern should not change - the realization and expression of divine love for all - and this poses an ongoing challenge for everyone pursuing faith in a higher calling.