The reason why religious symbols have been stopped from being displayed on government property is due to a total misreading and misinterpretation of the Constitution by the Supreme Court...it DOES happen! Government is not allowed to establish a religion, or itself as a "religion". This does NOT mean that if government allows a creche on City Hall grounds it is establishing Christianity!! nor does it mean it is establishing itself as a Christian entity! Religion, Christianity, Judaism, etc., - these are PROTECTED RIGHTS of citizens that the government is constitutionally bound to protect -- not restrict!
Atheism is not a religion -- it is anti-religion whose purpose is to antagonize the religious. Unfortunately, it, too, is protected by the Constitution as free speech. The difference, however, is that there is a line of offensive that should not be protected, especially at religious periods throughout the year when the atheists position is merely to denigrate and otherwise trample over the rights and protections of those who clearly are protected by the establishment clause and free speech/expression clause.