The reason government recognizes/endorses/fovors marriage is because it is the best way to produce and raise the next generation. Homosexual unions are incapable of producing and an inferior way of raising the next generation. Men and women are different (no matter how much the LGBT crowd tries to obscure the fact), and children do best with one of each in the house.
The debate is not just about "committed and loving relationships." You are free to have that if you want. Just don't try to call it marriage on your tax return, because it's not. The government does not have the same compelling interest to recognize homosexual unions.