Everson v. Board of Education is the case where SCOTUS interpreted the Constitution to encompass state action in the establishment clause:
"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."
You might not like it, but this interpretation of the Constitution is the law of the land. Scotus's interpretation states that the Second Amendment applies to self-defense, even though it is not actually stated in the Constitution. If you asked me does the Constitution provide for the ownership of arms for self defense, I would say yes. If you asked me does the Constitution prevent a state from establishing a religion, I would say yes.
Interpreted is the key word. It was a VERY liberal court. The decision is NOT the Constitution. Courts tend to have an agenda and this one did. The judiciary has been activist for some time. The Constitution is what it is no matter how someone tries to twist it.