What I believe:
1. Marriage is personal, a matter of the heart
1a. Legal marriage is mostly an artifact of religion.
2. Anyone should be able to marry anyone. Singular or plural.
3. The government should make no laws respecting marriage or the freedom to marry.
4. The government should get out of the marriage business entirely.
There is nothing which marriage laws cover which are not covered somewhere else in the law, except tax tables, which shouldn't discriminate against people on the basis of marital status anyway. I'm surprised the "married filing jointly" loophole has lasted this long. Where's the ACLU when you really need them?