The problem is that the government should have never gotten involved in marriage in the first place. From it's conception, marriage is a religious institution. The Fed got involved in order to give tax breaks to families. Now, the government wants to tell us what religious groups can call a family.
This is always the way of government: all it takes is a foot in the door and they will take over the whole house. This is the reason I'm against school vouchers: we let the government grace us with giving our money back and they will start mandating that private schools do the same things as the crummy public schools. The Fed gov needs to takes it's hands out of people pockets and laws out of areas that should be left to the states.