That attitude confuses me. It's a norm of professional behavior that is trivially easy to satisfy. Is it that much of an imposition that he not verbally curse in front of his coworkers? That's like a request that you come to work in the morning with clothes covering your belly button -- I mean sure, it constrains your options somewhat, but is it something to lose sleep over?

Mocking them about their religious convictions is also a bit more small-minded than I'd expect from someone working in a multicultural office. I shudder to think what would happen if he were exposed to someone with beliefs or behaviors a bit more exotic than a garden-variety evangelical Christian.