"Member of a country club" implies deliberate choice, at adult age, with full assent.
Mentioning in passing that you're a Catholic Christian has entirely different implications - it's most likely to be a set of values you got willy-nilly from your parents, that may have little practical implications on how you go about your life and work decisions. It would be absurd to rule someone out of a position based solely on learning that they're a member of this or that religion.
Maybe a workable tactic, if you're concerned, would be to say something like "Oh, by the way, some folks on the team you'll join are practicing Satanists, are you OK with that?". Let the narrow-minded select themselves out, religious tolerance goes both ways. ;)
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.