If we have a seperatation between church and state what ist he LEGAL argument for confessional priviledge.?

It depends on what you mean by "protected". The confessional privilege is a religious rule, not a secular law. And I think you'll find that if someone confessed of being a mass murderer or serial killer or of a bomb plot to blow up a building, that privilege would evaporate sooner than you could get out of the confessional box.

I am not a priest or a constitutional lawyer, but as I see it confessional privilege comes from the separation of church and state. I do not have the exact wording in front of me, however the first amendment guarantees the right to worship freely. The Catholic church requires confession and forbids the priest to break the confidence of confession. The law respects church rules.

Laws also respect religions which refuse military service, for example.

That said, how can laws forbid polygamy? What constitutes a legit religion? Do I have the first amendment right to form a religion which bans paying taxes?

Every state recognizes four privileges and some recognize five or six.

All states recognize husband-wife privilege provided it is clear to the spouse that the other spouse was confiding in confidence.

All states recognize attorney-client privilege.

All states recognize clergy-penitent privilege.

All states recognize physician-patient privilege.

Some states recognize psychologist/social worker -client privilege.

Some recognize reporter-source privilege.

The argument to privilege is that it is in society's self interest for people to be honest in these relationships. Confessional privilege in particular is a practical privilege. Since priests are bound to not communicate such information, the only effect of not having this privilege would be to jail the Catholic clergy en masse. At best you would get a lot of Catholic conversions in prison, at worst you could trigger an armed insurrection. There is no significant gain by granting state power and a danger to the state itself by trying to get that power. The legal argument is practicality and enforceability.

Courts will not enforce laws that will have no impact. Almost every state has adultery on its books as a crime. No state of the Union will enforce them on a public policy basis. Common law is the law of judges, not the law of legislatures. Such laws would be held as against public policy and voided in common law even if the legislature repealed the privilege.

I'm not Catholic. The US was not founded as a secular society. Read the compacts of the colonies.

The founding fathers stated that all men are endowed by their CREATOR with inalienable rights. Our rights come from God, not from the state. The powers of the state come from the people.

I believe that whatever a person tells his pastor should be confidential. But the pastor also should be able to make a decision as to whether or not to inform authorities of any criminal activity.

I don't believe in confessionals but they are a part of the exercise of the Catholic religion and as such are protected under the Constitutional right of freedom of religion. Priests are not allowed to tell anyone what was told them in the confessional. To put them on the stand and demand that they do would be a violation of the separation of church and state. The state has no right to interfere with religious rites.

A spouse cannot be compelled to testify against their spouse. Are you also arguing that spouses should be forced to testify against their spouse?

Maybe because they are in a private establishment, using their freedom of speech.

PS: Wouldn't it be kind of creepy using the Patriot Act in a church?

Because confessions to priests have nothing to do with the government...

It's not entirely without precedent, it could be argued as therapist-client priviledge

Not sure, but it's a heck of a good question. A star for you!