It was a good angle to have a rabbi argue in favor of a Christian display, but the problem is that he, like many believers, greatly distorts the atheist point of view. We're no angrier than the Rev. Martin Luther King Jr., Gertrude Stein or Simon Wiesenthal in the face of injustice. But we are resolute about enforcing the 1st Amendment.
I think city-endorsed religious displays are threatening and divisive in a pluralistic society such as ours. Displays on public property assume the weight and imprimatur of our common government. This is perceived as an endorsement of an individual religion by government, something clearly prohibited by the 1st Amendment.
We atheists don't hate Christmas, Christians or religion; we just don't want the government that represents all of us to give preference to particular beliefs.