So the main Mormon Temple is in Salt Lake City, Utah. Mormons are extremely conservative in general, and don't like the idea that anyone can walk down the main street in front of the temple dressed however they like and saying whatever they like. Since they can't violate the first amendment on public property, they decided to buy the street in question. Now they can enforce their rules because it's private property.
Don't get me wrong, I know a handful of Mormons. Some are among my best friends in the world. But as a religion, they are way off the deep end.