Gays: there is no reason not to. Therefor, I'm all for it
Polygamy: Against it. See the post of Froggo for my reasons. Added to it is the legal mess of the benefits that come with marriage. Also, it is mainly practiced (to my knowledge) by peoples who have an amassingly low oppion of women. The two seem to coincide quite a bit. And Mormons just creap me out.
Just because you THINK divorce would be messy is not enough.
You unjustly discriminate against those that can come to a amicable solution.
So that justification FAILS.
Incest: it is a proven fact that incestous relationships produce childern with severe mental or physical disabilities. So, there should be some kind of law concerning how closing two people can be related before they can get married. Not to mention how unconfortable family reunions would be after a divorce. **shudders**
This is about the gay right to marry on the sole fact of love.
Not about the consequences.