Q:"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof." Marriage laws, gay or otherwise, have no relation to this statement. Neither the state nor the church is damaged by any sort of marriage law. However, for a church to tell the state how to make such laws WOULD violate this statement. To ban gay marriage for religious reasons is to "respect an establishment of religion." To allow it is NOT to "prohibit free exercise thereof."
Government coercion to marry two people that any religion deems impossible or immoral. We’re seeing it now. Plus, marriage is intrinsically religious. If you notice, the amendment says, “No law respecting an establishment of religion.” Making a claim on what marriage is, regulating, and distributing it makes the government respect an establishment of a religion (what the religion is, i’m not sure, but nevertheless).
Get the government out of marriage and there would be no problem at all.