Federal welfare (foodstamps, unemployment, obamaphones, giveaway programs, etc) are unconstitutional. So is medicare, social security, etc. These functions are all reserved to the states and the people by the constitution. Likewise the federal government has no constitutional say in marriage or homosexualism or religious matters. Period. They cannot FORCE it on us.
If you give them the power to ban it then you give them jurisdiction over it. That means they can come around in a few years force it down your throat when the political winds change. You can’t have it both ways. Leave marriage to the states. Get it out of the tax code and quit taking favors from uncle fedgov for being married.