Do you really not understand the difference being allowing religion to be part of government and not having one single official religion? NO ONE is calling for the latter.
Well after reading this thread it seems to me that Soldier's question above is really the crux of the issue. The problem is that while the First Amendment doesn't specifically say word for word "freedom
from religion in government" it is specific that the government cannot establish a state religion. What I think is being overlooked is that the SCOTUS has interpreted that to mean that
religion cannot be the foundation upon which law or government policy is established. The reason why is because those with religious motivations will simply pass laws which agree with the tenants of their particular faith (say Catholicism) and after dong this for a while what you end up with is a Catholic government in everything but name.
In other words it seems to be argued that as long as no one comes out and passes a law saying that we are a Catholic nation then government has not established a state religion....but if the government passes multiple smaller laws that are based on Catholic belief then government has in effect become a Catholic entity. The SCOTUS realizes this and as such they have consistently maintained that if government wants to pass a law it has to be for some reason
OTHER than a religious one. So while the First Amendment doesn't say word for word "freedom
from religion in government" that stance must be assumed and maintained in order to avoid the establishment of a state religion by proxy.
This is why you don't see opponents of gay marriage argue before the courts that it is a violation of Christian belief. It's a flat out losing argument according to the interpretation of the First Amendment by the Supreme Court since its inception.
So essentially what it comes down to is: 1) Santorum has the right to believe whatever he wants and speak his mind. 2) Being a man of faith does not disqualify him from public office. 3) Whatever laws and policies he endorses had better be based on something
besides his faith or the SCOTUS will blast it to hell.