I would hire him if there was no superior candidate when it comes to job-relevant criteria.
The secret to toleration is realizing that, generally speaking, everyone is a horrible person by your standards, and so your standards are generally not useful in determining whether or not you should associate with people (all you do is punish people who got caught). They may be useful in picking your friends- but that's an entirely separate issue from who you hire.
There's a Mencken quote- "We must respect the other fellow's religion, but only in the sense and to the extent that we respect his theory that his wife is beautiful and his children smart. " - that seems appropriate. Let's say you find out in passing that your employee's wife is hideously ugly, and you work someplace where people sometimes bring their spouses to office parties or the office itself. How strongly would you be willing to act on your desire to avoid seeing his wife at office parties?
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.