I'm just glad none of these complaints seem to be coming from any of the games I worked!
I had a great partner and we worked four straight relatively problem-free games. There was one play I called where the coach asked for an explanation, we talked about it and he turned around and went right back to his position. In one game we had a rare batting out of order appeal to deal with (those pop up maybe once a year, if that).
The only play that got a little heated was on a batter-runner being called out for being out of the running lane and getting hit by the throw to first. This was in the late innings of a one-run game (the 12U championship game) so things were kind of tense at that point anyway. My partner handled it well and, after the game, several people that were arguing intensely actually came up to him and apologized (it probably helped that their team eventually won).
Personally, I have worked a couple of games with the gentleman that wears the outside chest protector and can't recall ever having any problems. That's one tricky thing about being an umpire. No matter how perfect you are, you are only one questionable call away from being "the worst umpire we've ever seen".