We have seen how people are treated for simply believing in traditional marriage and values. They are nearly destroyed by the LGBT community members. They are harassed, called the most vile names imaginable, ridiculed, and run out of jobs. What makes us think that these people will suddenly become pleasant and upstanding members of the community, simply because they are now allowed to marry a person of the same sex?
I am not saying that some of them are not pleasant or upstanding folks now. Some of them are good people. But that doesn't give them the right to change the structure of the family unit.