It's not even close.
It doesn't offend Atheists (at least the vast majority of them) for those reasons -- it offends civil libertarians because it goes against the First Amendment. Atheists and others are fine when government allows such displays for all religions or non-religions, just when they deliberately restrict it to one specific religion is where it becomes a defacto government endorsement of that religion.
You don't piss off Atheists for that -- you just show that you're completely mistaken. the US is not based off any particular religion's principles.
:9:
Nope. The Government cannot force a business to rename itself, no matter the "offense" taken. To think that the government would get involved in either of these issues is silly. And to imply that Saints is offensive to Atheists -- sillier.