Jack:
Plus, though I don't particularly like defending the Catholic church, they don't refuse membership to homosexuals or revoke the membership of couples who use birth control.
Even the claim that "[l]eadership positions are reserved to unmarried males" isn't entirely correct, if ordinary priesthood is counted as a "leadership position." Latin Rite Catholic priests indeed have to be celibate, but there are other Catholic rites that permit married men to become priests, and married priests of other Christian denominations who convert to Catholicism can be accepted without having to renounce either their priesthood or marriage (see here) for more detail). On the other hand, even in Eastern Catholic churches, bishops have to be celibate (just like among the Eastern Orthodox). An interesting question is what would happen if a married Anglican bishop converted to Catholicism; I don't think this has ever happened, but it seems like it will soon.
Let's say you are interviewing a candidate for a job. In casual conversation, the candidate mentions that he is a member of a rather old and prestigious country club. You've never heard the name of the club before.
You look up the country club afterwards, and are surprised by what you read. The club refuses membership to homosexuals. It revokes the membership of couples who use birth control. Leadership positions are reserved to unmarried males.
The candidate is otherwise competent. Under what conditions would you hire him? Would you want a law passed banning hiring discrimination based on country club membership?
(The country club is analogous to a nicer version of the Catholic church. I left out a couple bad things.)
Religious discrimination is illegal in many parts of the world, and I think that's probably a good thing. Still, keeping this at the object level (no meta-rules or veils of ignorance) it seems to me that discriminating against religious people is fine. I'm curious what other people think.