My tax dollars go to provide the health benefits for the spouses of federal employees even in those cases where, for religious or philosophical or moral or political reasons, I do not approve of their marriages—for instance, when they are third or fourth marriages, where they are marriages of persons who had previously been adulterously involved, where there are no children, etc.
No one objects that such marriages, which lie outside the realm of traditional marriage, should thereby not qualify the spouses for benefits.
By parity of reasoning, your tax dollars should go to provide benefits for same-sex spouses or partners of federal employees.
It is time, perhaps, for an even broader definition of something like civil partnerships. I am thinking here of something like the solution tried by the Archdiocese of San Francisco in 1997—if I recall correctly—when faced with a city law that would require them to provide benefits to same-sex partners in spite of the way that this flies in the face of Church teaching about marriage and sexual morality. The solution? They decided that every employee could designate one other adult, beside any dependent children, who could be the recipient of benefits. This could be a spouse, a partner, a relative, a friend. Since every employee got to designate one person, it was utterly fair and no one had to approve of any marriages that they found morally reprehensible.
Quite apart from the religious uses of marriage, one great benefit of marriages and partnerships and even deep friendships is that they tie us more closely together and thus make us all more stable members of society.