To those opponents of gay marriage?

Do you believe that the constitution is the supreme law of the land? If so, how can you defend blocking marriage licenses from other states when the constitution explicitly has a full faith and credit clause stating "Such Acts, records and judicial proceedings or copies thereof, so authenticated, shall have the same full faith and credit in every court within the US and its Territories and Possessions as they have by law or usage in the courts of such State, Territory or Possession from which they are taken" In other words, any license granted in one state is valid in all states. So please explain to me your position. Does that mean that the constitution can be ignored wherever convenient?