Research Report shows, the majority of Americans...of all faiths, or no faith...actually favor Same Sex Marriage. The USA is a pluralistic society that supports each citizen's right to "Life, Liberty and the Pursuit of Happiness"...and I'll add, "So Long as No One Else is Harmed"...Same Sex Marriage does not harm anyone, or deny them their religious freedom to practice their religion. If it's a tenet of your religion that membership requires heterosexual marriage, so be it...but it is wrong to apply your religious beliefs to all other citizens of this country...especially when you're in a distinct minority.
Link: https://www.pewresearch.org/religion/religious-landscape-study/views-about-same-sex-marriage/