Sorry, but as a lawyer, I can't agree with you there. The first amendment doesn't have a "freedom of religion" clause. Rather, it has two separate religion clauses, which can be at odds with each other: the free exercise clause (which I suspect is being used at least in part as justification for this law), and the establishment clause, which I think is what you're saying this violates.
But although I am not defending the law, I don't think it even comes close to violating the establishment clause. This law neither favors one religion over another (and wouldn't it be fun to see, say, Muslims use it in ways that infuriate the right?) nor requires anyone to comply with any religious principle or belief whatsoever.
You have no right to be free from the religious expression of private parties, no matter how odious you find their beliefs.
The 'establishment clause' does not allow for the passing of any law that recognizes a religion. ANY religion.
The Establishment Clause is a limitation placed upon the United States Congress preventing it from passing legislation respecting an establishment of religion. The second half of the Establishment Clause inherently prohibits the government from preferring any one religion over another; which tends to allow for a greater harmony amongst all of the many denominations in the United States. While the Establishment Clause does prohibit Congress from preferring or elevating one religion over another, still it does not prohibit the government's entry into religious domain to make accommodations for religious observances and practices in order to achieve the purposes of the Free Exercise Clause.
Since many religions DO support gay marriage, and have no issues with gays, the State if Indiana directly supported a religion by passing this law therefore violating the establishment clause.
Either way, the State on Indiana just did what Sharia Law would have done. They have segregated a portion of our current society for the removal of their rights. There is nothing constitutional about that.
Listen, I'm not a fan of gays, or gay sex, but since I am not the former, and don't engage in the later, I really don't have a say in it.
Marriage is a merger, a 'legal construct', the legal joining of two lives, for legal benefit to each person in said merger.
I've known many gay couples that have been together for tens of years, and put many of the heterosexual marriages to shame. When we get into deciding if someone loves another person well enough to merit the award of marriage, many heterosexual marriages would be nullified.
Heck, Newt Gingrich is on his, what, third wife, maybe forth? Rush Limbaugh is on his fourth, and was arrested for attempting to smuggle hundreds of Viagra tablets to a country known for their marketing of young boy to rich men for sex.
So, try to say that gay marriage devalues 'traditional marriage'. You don't have a damn solid leg to stand on.
And 'traditional marriage' isn't even the same as it was in those much lusted after 'biblical times'. It's been redefined many times.
Indiana, and potentially Alabama, are departing on a dangerous course. Incorporating hatred, intolerance, and bigotry, is no way to run a state, or a country. Well, unless you want to install Sharia Law in the United States.
Because if nothing else I say sinks in, think about what could be next.
Making smoking illegal? Drinking? (Oh, they can think of doing that again, especially if hatred and bigotry are installing in state laws and constitutions) Extramarital sex? Sex toys? Walking with anyone not related, or married to a woman?
Sound familiar?
Be careful...