I support separation of church and state. Marriage is a religious institution. All people, gay or straight, you should only be recognized *legally* as being in *civil unions* There should be one federal regulation that consistently applies to everyone in a union, in terms of benefits, rights, et al. Gays and straights should have equal rights under such a Federal Civil Union statute.
When it comes to marriage, that's a religious matter, and it is up to various religions to decide whether they want to permit same-sex "Marriage".
That said, I am against a "gay marriage ban" in the constitution. Why? The constitution is a document that traditionally grants freedoms to individuals, primarily, by restricting what the government can do. Here we are, adding amendments into this great document for the sole purpose of *removing freedoms* from people. (except for the income tax amendment)
I view a Gay Marriage Ban amendment precisely as I view Prohibition. It's a big mistake, and like prohibition, it would be a waste, because eventually another amendment would be passed to rescind it in the future.
Ultimately, this falls to the states. Why do people in Tennesee care if people in Boston allow same-sex unions? Live in your own state, leave others alone. Vive La Difference.