Glove-slapping when you are getting tagged is a part of the game. You are supposed to be a little more subtle. A-Rod did it badly on that play, but it was a desperate move.
It's just like sweeping your foot on a slide to try and break up a DP or get a steal. You are not supposed to do it, but if it is subtle enough, it is not a big deal.
I see what you are saying about little leaguers hearing that A-Rod would push the rules to win, but I don't think that is as bad of a message as you are making it here, certainly not as bad as your other examples.
I have been a Red Sox fan since I was a little kid rigging up a clothes hanger to my UHF to tune in TV38. I didn't want A-Rod last winter so much, and I thought 'the slap' was the right play at the right time.
In a strange way, them winning the Series has made me less of a Sox fan. Glad it was the Yanks they beat, though.