They should have equal rights in terms of their union, but in terms of procreation and furthering the species etc, how can they?
Racism doesn't really have such an argument does it.
I just don't see why the word matters all that much. Surely as long as you are equal in the eyes of the law, why not have a different word to mean same sex marriage? Then if you say "joe is married" you don't have to ask "to a woman? or another man?".