I just wanted to archive this response I made to a thread on skeptalk, where a user has asked, somewhat naively:
'[...] why "in God we trust" or "One nation under God" upsets atheists'
Well, the first thing for me is that it's just a lie. I'm not sure about you, but I was brought up to believe that lies are a bad thing. There's no evidence for a god. None. To make such claims without evidence falls into the "lie" category for me.
The second thing is that such a statement is counter-constitutional. Not that I actually have standing to talk about US issues, of course, but we have some quite similar problems here in Australia. Our constitution's establishment clause was modelled on the US's clause, but has been interpreted differently by some courts. There's a challenge going through the high court at the moment against government-funded chaplains in schools, something which I strongly object to. I don't care if a private school has them, but government-funded public schools certainly shouldn't.
Of course, we're not stupid enough to put "one nation under arbitrary imaginary being" or "in tooth fairy we trust" on our currency, but it wouldn't surprise me if such a measure got proposed in parliament at some point.
The third reason is that there's an implied social rift inherent in such statements. If you don't fawn and grovel to magic sky-daddy, there's an implication that you're not really part of the nation. Which is, of course, entirely untrue.
The fourth reason is smug dumbass theistards that attempt to use such slogans to clumsily bludgeon the non-christian bloc. "We're one nayshun under GAAWD!! Get out if'n you don' likes it!', they say. Fuck you, you mouthbreathing inbred waste of skin and organs.
We have that here too. There are "christian country" idiots all over the place, and they often try to imply that atheists are somehow unaustralian or unwelcome in "their" country. Fact is Australia has never been a christian country. Same for the US. It's never been a christian country. It's been "a country with a majority of citizens professing christianity", nothing more.
But at the end of the day, they're just highly visible symptoms of the underlying disease - which is expressed so clearly in the common-or-garden variety theist - of absurdly simplistic, disconnected, fallacious, introspection-free and unstructured thinking. Or, colloquially - "people are stupid and it annoys me".