The communication problem is that theists simply don't accept the atheist premise that there is no proof of a god. They cite Bible (or, presumably, Koran) verses that reinforce the idea that everyone knows, in a very real way, that there is a god. For an atheist to exist, therefore, a specific and deliberate rebellion has to occur.
Theists should know that this is patently and profoundly untrue, but if they insist on holding this position, then an honest discussion of the subject of god really cannot take place. Not only is it relatively insulting to be told that I am lying before I even open my mouth, but it also assumes my position without listening to me. In other words, if a theist comes to a discussion with this thought in his or her head, then there is no need for the atheist to even show up.