They called a balk because Rizzo was moving towards the plate(to field a potential bunt) when Hendricks started a pickoff throw, and therefore was throwing to an unoccupied base, even though Rizzo was back at the base by the time the throw got there. In the most charitable interpretation the ump is calling something that is against the spirit of the rule and never called in practice, in the more likely interpretation he straight up blew the call and rang up Maddon out of partial embarrassment. I've seen it called in high school and lower from time to time, but usually in a much more blatantly unoccupied base fashion. Never when the 1b was only a step or two in front. I agree, the umpire overreacted and called something that shouldn't have and then issued the ejection because he did not want to be called out on it. It was bush league and if the kid can't handle himself better, he needs to go back to umpiring high school ball.