to “protect the constitutional principle of separation between state and church
There is no Constitutional principle of seperation. That is a judicial ruling of a modern day court. Nothing in the Constituion seperates Church and State.
Unfortunately, once an interpretation has been made, it opens the door for further "movement" on whatever issue, which again leads to another, and so on, and the end result is this ridiculous situation. The plain words of the constitution are that "Congress shall make no law respecting an establishment of religion" which is clearly an injunction against the setting up of a State sponsored or approved religious structure aka England (and many other nations too as it happens). However, it can (and has) been interpreted to mean that the U.S. government should not prefer one religion over another, and therefore it is wrong for Public squares to have Christmas trees, as that way the State is "preferring" Christianity over other faiths. Of course, the ultimate result of this kind of interpretation is that ALL christian activity will be criminalised. Now as an interpretation this is clearly a stretch. There effectively WERE no non-Christian religions in the US when the Constitution was drafted and the fact that a time would come when there would be was not anticipated, or rather it wasn't exactly at the top of anyones agenda. But, this is an interpretation that suits the new hightly militant atheist movement. And that is the nub of the matter. They don't give a toss about the legal niceties of how society and State relate to each other. They are simply pushing their own agenda (the ultimate destruction of all religion) and this is a convenient tool to use to do that.