My sense of etiquette begins and ends with doing what works best for the kids.
This is a complicated situation that can swing one way or the other depending on circumstances. Possibly your reaction to coachp's post is part of the problem. You asked if you were wrong for being upset, and he simply stated his opinion about being opposed to one coach being the "only one" to work with a group of kids. I really think his point is that kids come in all mental shapes and sizes that can't be properly tweaked (for the child's benefit) by any one coach.........
So you play the "negative" card????
" its not about coaches not being able to work together ... figures someone would look for the negative....."
Maybe this is more about working with other coaches than it appears? You gotta admit that when two coaches spend some time together that one thing almost always happens. One, or both, learns a little bit from from the other.
None of us is the complete package. Those coaches who think they are will often prove themselves wrong and end up wishing they'd accepted help from others and been better at building bridges with other coaches.
So unless you're all that and a bag of chips you should approach this coach, offer a reserved "thanks" for their help, and ask them what they've offered to the kid. If they answer (in essence) that they were filling in a few gaps that you'd over looked, then maybe you should spend your time finding out what this coach knows that you maybe don't.
The point is, you and I both have discovered things we were doing that didn't work as well as other things. We then tossed the old thing out and started using the new thing, but doesn't it seem ironic that up to your most recent discovery discovery you believed the "old thing" to be the best thing?
Don't let what *you know* prevent you from learning from others as well as from yourself.