To be fair to the ump, if you look at where he was standing, he couldn't see how softly the ball was thrown, because the SS was standing with his back to the ump. So he didn't have a good look at the play. I'm not going to argue about it (this season is no longer worth arguing about many things), but as a major league ump, its his job to get in position to see the play clearly and make the right call.