Most People in America Still Believe in Equal Rights
There are those who argue that only a "mommie" and a "daddy" should raise a child, because only a mother and father household provides the right combination to raise healthy, happy, children, and of course we all know that heterosexual parents NEVER have gay children. So there are those who argue that if gay couples raise children they will create gay children, just as heterosexual couples create only straight children.
Further, once the military's ban on gay/lesbian soldiers was lifted, the armed forces have done a breathtakingly quick job of supporting gay and lesbian soldiers; and perhaps as soon as ordinary people saw that none of the dire predictions of politicians like Rick Santorum came true, it was another step to see no reason to deny that LGBT issues were civil rights issues. A side note: it is interesting that Rick Santorum never served his country as a soldier, and yet he spoke about order, morale, and discipline in the military, as if he had a clue.