Other than awareness of our mortality, the thing that makes us most uniquely human is empathy. From empathy stems morality, and the most instinctive understanding of the difference between right and wrong.
It's ironic that, particularly among Christians of the right-wing persuasion, empathy is so notably absent. It couldn't be more clear: one need only look at their legislative proposals.
Empathy not only requires no religious view; when one looks around the planet it's pretty obvious that religion seems to rob people of that capacity. There is, in other words, no requirement for religion to act honorably and it may well be that the opposite is true. What, after all, could be less moral than acting in a "good" manner because one expects eternal reward for doing so, or fears eternal punishment for not? Empathy leads to doing right by oneself and others simply because it's right; no other reason required. No expectations other than the satisfaction of self-respect.
Which is why the ridiculous claim that atheism equates to sub-humanity is so, well, ridiculous. And, I guess, lacking in empathy. Religionists are those unwilling or unable to accept the world as it is, and to live with uncertainty. It may well be all too human to lack those capacities, and I don't begrudge it for those who need it; but to suggest that those who (to paraphrase Richard Feynman) prefer to live with doubt over believing something that might be wrong are less than human is the height of arrogance. And exhibits a fundamental misunderstanding of what it is to be human.
I don't identify as "atheist" any more than I identify as "foodist" or "respirationist." To me, the default assumption ought to be that humans are atheistic: religion is a construct, needed by many, to explain certain unexplainables, the absence of which leave them feeling a little nervous. To see that the planet is home to scores of religions and believers in thousands of different gods and godettes is proof that religion is a construct. That there's no "right" one. For any religious belief there are literally billions of people who believe just as fervently, just as unalterably, in something entirely different. Clearly, it's a very human need. But it does not follow that those who don't need it aren't human.
One could make a compelling argument, though, that those who manage to live a life of empathy for their fellow humans, who try to do as right by them as they'd have done to themselves, without believing in the unprovable, who are able to revel in the wonders of life, feel its connections because it's so obvious, undiluted by magical thinking, are a tiny step closer to the next level. Is how I see it.