Religious organizations can discriminate (with limits) for religious practices. At least in the US, there's a carveout - for example, a Catholic church can't refuse to hire a priest because he's black, or because he's handicapped, that would still be discrimination... but they can refuse to hire him if he's a Muslim, or if he's a Baptist, or even if he's married, because that directly conflicts with their religion.

But even with that, there's no legal protection of your right to kiss someone, or your right to sleep with someone, at least as far as membership in a club goes. You can't be thrown in jail for kissing someone on your college campus, but they're within their rights to kick you out, if their own rules say you can't do it.

That doesn't mean the rest of us have to like it, or even approve of it, but it's not actual discrimination.