Who gets to decide what’s a “little” sin, and legislation subject to constituional constraints, and which ones are the “big” sins that get a pass?
If they pose a threat to people and to society, they’re “big” sins. Thus, gay marriage, abortion, murder, embryonic stem cell research, cloning, and euthanasia out to be banned.
By the way, are we arguing over whether it should be banned period, or whether it should be banned at the state or federal level? Because if it’s the latter, the states DO have a role in the amendment process, so banning it at the federal level would not ignore the states (see Tailgunner Joe’s post).