It is basicall interpretation
There is among a certain kind of atheist a partronizing view towards theists, that you must not say anything upsetting to the theist, lest he be irrationally angered. In this case, I find the refusal to be honest a patronizing trait. The logic seems to be that, well, since it's obviously impossible to get theists to discuss anything rationally, even uttering a hint of atheism is horribly divisive and somehow counter-productive.
It reminds me how many of the most virulent anti-gay rhetoric on the right-wing comes from self-hating closeted gays.
And yes, the anti-atheist reacion you so commonly see is because the people in the minority are terribly upset that their world-view is no longer placed in a position of moral superiority.
p.s. I hate these damn spam-blockers that are impossible to read