Not in all cases. When it's part of a larger display, and displayed primarily for historical ends, it's allowed. When it is classified as an establishment of religion, it is not allowed. As was decided in McCreary County v ACLU, which was issued the same day as Van Orden v Perry.
Justice Breyer was the swing vote in both those cases--his concurring opinion made the difference in Van Orden. Far from wrapping up the distinction in a neat rule, as you seem to want to do, he emphasized how these cases call for a subtle analysis of the facts to determine if the effect of a display is inconsistent with the values the First Amendment's two religion clauses express. Deciding each case on its particular facts is just the opposite of applying an established rule--it's what courts do when they do
not have any clear rule to follow.
The Court's Establishment Clause jurisprudence is as unclear and difficult as it gets. Lots of things seem to be governed by clear little rules to people who have very little understanding of them. Read Lynch v. Donnelly and Allegheny County together, and then explain to us exactly what the rule on Christmastime displays in public places is. That is, if you can.
And I wonder how you would fit Capitol Square Review Board into your rule about the Establishment Clause question turning on "part of a larger display," "primarily for historical ends," etc. The Court held that crosses the KKK was allowed to erect on public land across from the Ohio state capitol did not violate the Establishment Clause, and yet they were neither part of a larger display nor displayed primarily for historical purposes. Tell us how that squares with McCreary County.
Atheists have no problem recognizing that the colonies were inhabited by people fleeing religious persecution...
Escape from religious persecution was only one reason people first came from England to America, and it played no part in the decision of many of them.
or that some of those colonists turned right around persecuted some of their own citizens on religious grounds. By preventing the government from establishing a state religion, citizens would not have to fear a repeat of that kind of persecution from their own government.
I don't think that's a very accurate statement of the motivation for the Establishment Clause. A number of the states had their own official religions, and although enforcing them had caused a lot of resentment, that hadn't made the states generally abandon the idea. But even granting there was general agreement in 1791 that the United States should not have a national religion like many other countries had, it's far from clear the Establishment Clause was meant to prevent the federal government from generally supporting Christianity. I'm not going to debate here how much the Establishment Clause was meant to do beyond prohibiting an official religion--but the question is highly debatable.
A 6 foot monument ordering you not to commit adultery is your idea of fun?
Ah, what wit! Adultery has traditionally been a crime in most states, if not all. If the majority of a state's residents want to promote their belief that adultery is immoral and unacceptable by making it a crime, that's their business, and no one else's. What I personally think of the commandment against adultery, adultery laws, etc. is irrelevant.
My concern is the right of Americans to celebrate and promote traditional American culture and values in the face of harassment by America-loathing atheists who ironically call themselves "liberal." What they really are is today Puritans--self-righteous, close-minded prigs who want to boss around everyone they think is less morally enlightened than they are.
Everson expanded the separation of church and state from the federal level to the states. This extension was, in many ways, more important than the actual decision itself.
Again, that's not an accurate statement. Everson was the Court's first real Establishment Clause decision, period. So it had no cases declaring any separation of church and state to expand to anything. It was only in Everson that Justice Black declared that phrase from Thomas Jefferson's letter to be the law. Everson applied the Establishment Clause to the federal government and the states at the same time.
As to the "flexible barrier," it's been nearly 70 years of courts trying to balance the need to separate church and state, and other issues such as freedom of expression. I doubt you'd be happy if the courts sided exclusively on the side of separation, at the expense of other rights.
Right idea, wrong freedom. It's not the freedom of speech that overly strict interpretations of the Establishment Clause threatens, but the right to free exercise of religion. As the Court has discussed (in Zorach v. Clauson, for example) there is some tension between the two religion clauses, so that pushing the Establishment Clause too far may violate the Free Exercise Clause.
If a fire breaks out in the kitchen at First Baptist as the ladies in the flock are busily preparing for the church bake sale, shouldn't the city fire department just let it burn? After all a municipal government is only a creature of the state where it's located. And if the Establishment Clause means strict separation of church and state, we can't have the state government helping a church, can we?