It shouldn't be a rule and I can't see how anyone who's played or been around the game long enough can defend it.
I have played all my life and always thought the slides they let go at 2nd were stupid. Guess I am in the minority on that. I also hate the "slides", or should I saw tackles that they allow (or allowed? think they changed it some) at home. Maybe it was because I was a catcher though, but I know a few people I went out of my way to injure because they tried to run me over at home instead of sliding. Now I have yet to see a replay of this slide, but if he went out of his way at all to disrupt the throw beyond sliding hard towards (and I don't mean he could knick the bag with his fingertips towards, I mean full on top of the bag) the bag, then I am fine with the call. Raising his arms a stupid amount and making contact would count as going out of his way imo. No need to take it that far just slide hard and make the guy have to jump enough to disrupt him that way.