Actually I have no problem getting the government out of the Sacrament of Marriage.
Marriage (and the family) is a natural institution as well as a sacramental one, and the State has a duty to defend it.
Sodomite "marriage" isn't about civil rights but about the right of children to be raised by their natural parents, and in extremis, to be adopted by a married man and woman.
The phenomenon of separating the marital act from procreation through induced sterility (a.k.a., "birth control") has served to obscure one of the two defining principles of marriage, procreation and the mutual care of the spouses.