I would say, without a shadow of doubt, outing yourself as an atheist is more damning here in the southern US. I work with two gay men on a semi-regular basis who are contractors for our firm (they are both quite christian aswell, although the non-denominational god-is-love type) and nobody bats an eyelash or even has an off-color remark when they leave the room. Non-christians, on the other hand, draw quite a bit of criticism and I shudder to think of the atheist reaction.

When I read the poll saying that Atheists were the least liked/trusted group in the US I certainly didn't think it was an exaggeration. While the gay community may well be marginalized, they have a much longer standing and widely accepted support network. If you are fired because you are gay, someone will take your case immidiately. If you are fired because you are an atheist... well, I don't intend on finding out what happens there.