Relatively recently, Mormons made their stance against gays and lesbians more explicitly unfriendly. However, according to the New York Times:
Mormon leaders have parted company with the leaders of evangelical and other conservative churches by affirming that despite their religious convictions, even people of faith opposed to gay marriage must follow the law.
Mormons have long had different ideology than the mainstream, which inclines them toward their views on external “law of the land”/render-unto-Caesar and then their own internal rules.
Everyday evangelical Christians are opposite. Since they’re in the mainstream and have long been the majority, it’s understood that they’re the ones setting the law. Baptists and their ilk don’t view the law of the land as an external thing, but a thing that was made for them, by them, and they adhere to for that reason.
If you read the news, you’ll find a lot of instances where Mormons do surprising things. I would contend that it’s because they have an inherently different view of the world than your average Christian.