There's no common ground between atheists and theists. That's not precisely true: There is a common ground, reality and evidence. It's just that atheists and rationalists stay exclusively on that common ground; religious people stray outside of that common ground. The conflict between theists and atheists is ineluctable and irreconcilable: we are not going to give you permission to stray out of the bounds and call your infantile fantasies reality.
I don't think very many atheists really care what theists do in the privacy of their own homes and their own minds. I know I don't really care. I do, however, care about the social privilege of theism. Hang a "rabbi" or "priest" or "reverend" after your name, claim some special privilege to speak for God, and voila!, you're an authority on ethics, politics and sometimes even economics. Take the "reverend" off your name, speak for yourself and not for God, and maybe I'll take you a little more seriously. You have the "right" (such as it is) to be as foolish as you want on your own time; bring your foolishness out in public and I'll slap it down.
The conflict is especially important about ethics. If you're saying the exact same thing as a secular, rational, caring humanist, then who cares that you call yourself "religious"? You are, like Einstein, just using "god" as a metaphor for the natural world. If that were all, or even mostly, what "religious" people did, there wouldn't be an atheist movement.
The only time religion actually matters is when you want to call something "good" or "bad" that a sane, rational, normally-socialized secular atheist could not rationally assent to. You just cannot justify the oppression of gays, the subordination and slavery of women and their bodies, and the social and economic parasitism of millions of priests, rabbis, imams, mullahs, ministers, and Scientology auditors on any kind of rational, humanistic ground. You have to bring God or some other persistent delusion to make your case.
Atheism does not just hang there all by itself; it usually comes from rationality, skepticism, a scientific mindset, a humanist emotional makeup and ordinary civilized socialization. Atheists are on the whole just skeptics who have applied their skepticism to claims about the supernatural. (There are, of course, atheists who are not skeptics, but you have to dig hard to find them, and skeptical atheists such as myself have as much disdain for non-theistic delusions as we do for the theistic variety.) We are against delusion; we call ourselves atheists because we focus on the specific set of delusions that constitute what is usually labeled as religion.
If you attack me, and if you attack me for being an atheist, then you are attacking my vision that ethics ought to be informed by the facts, not just about the world outside our minds, but the content of our minds as well, our minds that are just as much a part of the real, physical world as rocks and trees. Attack all you want, I may be wrong and if I am, I want to know about it. But when you attack me for "intolerance", you are attacking me for what I consider to be my strongest and most important ethical belief: I am indeed absolutely intolerant, and damn proud of my intolerance, of lies and bullshit, of delusion and fantasy used to justify oppression, exploitation and parasitism. If you yourself are similarly intolerant, we have no dispute. If you are not, too bad for you.
If you want to define your religion into triviality, vacuity, irrelevance, myth, metaphor, i.e. into exact substantive agreement with atheism, then be my guest; you will have stopped talking about the kind of religion I'm against. The Gnu Atheist movement is not in the business of literary criticism; it's a political, ethical and social movement.
You might say, "Hey, I just use 'God' to contextualize the wonder and mystery of the natural world, our biologically and socially evolved empathy and fellow-feeling, and our civilized standards of behavior and governance. We agree on every substantive point."
I would then reply, "Fine. I think it's a stupid metaphor, but I have better things to do than criticize your taste in literature. Let's join forces and attack the bastards and their billion followers who justify oppression, domination, inhumanity and suffering by appealing to a supernatural deity that is manifestly delusional."