Government benefits should only be tied to civil unions. The government should get the hell out of marriage and couples can determine if they want to consider themselves married.
I would never say that changing the definition of marriage is blatantly unconstitutional. The constitution says nothing about the right of two people of the same sex getting married nor does it say anything about traditional marriage. You could argue equal protection under the law, but as it stands a heterosexual man and a homosexual are both legally not permitted to marry a man. Blatantly is absolutely the wrong word to use.
Also, your insinuation that religious people should not use their deeply held beliefs to influence the societies in which they live is disturbing. You have a vote and they have a vote.