And the someone loves their dog, their sister/brother? Should those that suffer from other mental disorders have the state sanctioned right to marry someone with the same disorder? Should bleeders have the state sanctioned right to marry?
We have a society to keep stable, here, for the good of all therein. Sanctioned and institutionalized homosexuality is either a major contributor to the destruction of non-invaded and conquered cultures in the past or an indicator it is crashing.
The sign of it is never good whether it is the engine or the speedometer.