You do realize that the language of Madison's original draft of the Establishment Clause, was not so friendly to unbelievers, and in fact provided all beliefs with protections not afforded to non-believers. This and no less than two other drafts were struck down by the first Congress, before settling on the version seen today.
The Establishment Clause, stating that "Congress shall make no law respecting an establishment of religion", as well as the Free Excercise Clause, "... or prohibiting the free exercise thereof", basicly prohibit the government from supporting any religion through legislation, or preferential treatment, unless Free Excercise is being impinged upon.
Unless the government intends on displaying all religious symbols upon request, they cannot show preference by displaying any particular religion's symbols permanently on publicly owned land. In other word's government displaying preference was never legal, but was tolerated in times when it was harder to hear a minority voice.
Nobody's telling you you can't wear a cross, or go to church on Sunday. You're free to preach as long as you obey all local ordinances (loitering, trespassing, harassment, just generally respecting others), and don't impinge on other people's Free Exercise.
Justice Hugo Black in 1947 stated that:
'The "establishment of religion" clause of the First Amendment means at least this: Neither a state nor the federal government can set up a church. Neither can pass laws which aid one religion, aid all religions, or prefer one religion over another. Neither can force nor influence a person to go to or to remain away from church against his will or force him to profess a belief or disbelief in any religion. No person can be punished for entertaining or professing religious beliefs or disbeliefs, for church attendance or non-attendance. No tax in any amount, large or small, can be levied to support any religious activities or institutions, whatever they may be called, or whatever form they may adopt to teach or practice religion. Neither a state nor the Federal Government can, openly or secretly, participate in the affairs of any religious organizations or groups and vice versa. In the words of Jefferson, the clause against establishment of religion by law was intended to erect "a wall of separation between church and State."'
