I did not suggest covering your partner's ***. It was a bad call, no doubt about it. Humans make mistakes. Bad calls are part of the game. This one you can't change - fair/foul is, by rule, a judgment call. Screw the kid out of a hit? It's a do-over. You're giving him a chance to get another one. 6 year-olds don't care about the score, who wins, or their batting average. 6 is also a perfect age to learn that sometimes umpires blow calls, but you accept it without whining and move on. Both coaches should be setting that example, and if either one of them came out to argue, he would be on a short leash.
But I know your intentions were indeed honorable, and we can agree to disagree.