Re: Christian, and it's obvious religious ties
Well, first off, grace has a lot of different connotations besides the Grace of God. Physical grace, graciousness, favor, etc. (It's even used sarcastically when someone does something clumsy or has a silly accident. "Nice going, Grace.")
As for Christian: remember that a lot of people don't specifically call themselves Christians or go in for the church, Bible study, etc, but do things strongly associated with Christianity, like christening their babies, choosing godparents, celebrating Christmas and Easter.
So a not-strongly-religious person naming their son Christian isn't actually odd. Not as odd as, say, a Jewish person doing that.
I don't think even a minimally well-adjusted person would be put off by meeting someone called Christian even if their own religious views were very different or they had a beef with the religion. For one thing they'd surely recognize that the name wasn't self-chosen.
In real life, changing one's name legally and officially isn't all that common. A Christian who later became an atheist (or a Jew or a Muslim) might well do so, or just go by Chris like he always has, or maybe just start going by a middle name but not bother to legally change his name. Or he might hang onto the full name and act all ironic about it, but if so I'd expect him to be an atheist rather than some other defined, practicing faith; that would be kind of a big F-U, on -purpose move.
Before you criticize a man, walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes!
Steve Martin