No where in the constitution is this often quoted statement, however what the constitution does say is that the "government shall make no law", concerning religion.
What the courts have declared and what the intellectual community accepts as fact simply does not comply with this simple precept, and also goes against the judicial systems desire to legislate from the bench.
The reason I bring this up is because I agree with the rest of this article explaining the differences in party attitude we have here in the U.S.. From Daily Kos: State of the Nation.
I believe that the liberal political perspective focuses its application of values in the public arena, eschewing the impulse to dictate how people should live their private lives and what their personal moral codes should be.