Imagine, for a second, that you're one of the people tending Temple Square in Salt Lake City. Your actions, fairly or unfairly, reflect on your church as a whole. You see a gay couple walking through, and they kiss. Do you: a) let it go, b) approach them and let them know that your religion frowns on such things, or c) have them cuffed and thrown off the property?
Of course, I wouldn't be posting had the folks in question chosen anything but option c).
I'm willing to give the Church the benefit of the doubt here and say that they were thrown off for kissing, not for being gay. Having never kissed anyone in Temple Square, I can't speak as to the veracity of the "no PDA allowed from anyone" claim, but considering the primacy Mormons place on chastity, and the intensity with which this ideal is pursued, I can believe it. And the Church didn't overstep its legal bounds; it has a right to throw you off if it wants, and doesn't really need to give a reason for doing so. Temple Square is private property, after all, and trespassing laws (which I'm okay with) apply. The couple broke a law when they were asked to leave and did not do so.
But dude, throwing someone off for kissing is just dumb PR. Throwing a couple off Church property for making out and groping one another is one thing... doing the same for a little good night kiss is another. (And when there's a doubt, as there is in this case since the AP reporter didn't really go into details, err on the side of letting it go.) Seriously, under Monson the Church has had the approximate PR acumen of a jelly donut, which is the exact opposite of what the LDS Church needs right now.