There's a very good essay in the WSJ written by one of the attorneys pushing to overturn California's prop 8 at the federal level. He makes some very good points, and takes on some of the anti-gay arguments that aren't, and have never been, valid.
By contrast, there is no legitimate state policy underlying Proposition 8. The occasional suggestion that marriages between people of different sexes may somehow be threatened by marriages of people of the same sex does not withstand discussion. It is difficult to the point of impossibility to envision two love-struck heterosexuals contemplating marriage to decide against it because gays and lesbians also have the right to marry; it is equally hard to envision a couple whose marriage is troubled basing the decision of whether to divorce on whether their gay neighbors are married or living in a domestic partnership.It's worth a read and the entire essay can be seen here.
If we were prepared to consign minority rights to a majority vote, there would be no need for a constitution.