"So long story short you have to do some fact gathering first to try and determine if the coach is right or wrong. That will dictate the tenor of any further communication."
Did you completely brush over what I said? As you can plainly see my suggestion was he get the facts before doing anything rash. I just don't see how you take my post and run with it in the direction you did. That is what causes so many arguments on here. And causes people to just go away. I have pretty thick skin however so I am not so easily dismissed but others just decide the site is not worth their time and aggravation.
Let me see - you mentioned ZERO reason to trust the coach (in other words, doubt the coach until somehow you determine that you no longer have to) and then state that your video analysis will "dictate the tenor of any further communication" once you decide whether the coach is right or wrong. In my world, the coach gets to dictate the tenor. You postulate that the parent/kid comb, maybe in partnership with some private coach, should make an assessment of the coach based on whatever litmus test you decide upon (your definition of "correct" - as there is often no consensus) Please correct me if I am wrong, but you are basically saying the coach should be put on the defensive and everyone on the team who has received recommended changes should seek some third party validation before proceeding. In some strange situations, that might work, but for the vast majority of high school programs, the coach will have zero patience for some kid who says they will get back with him on the appropriateness of the suggested changes - let's go to the video first!
What if, during a game, the coach signals for the kid to steal. The kid, using his own book of wisdom, decides that attempting a steal is not ideal and signals back that he is staying put. To most everyone, that would sound crazy. Telling a parent that the high school coach needs to earn the family's trust - after the kid make the team - is not far behind. If you have so littel trust in the coach, don't let your kid go out for the team. There are lots of ways to discuss the changes and their effects on current mechanics, but throwing out phrases likes "zero trust' and "dictate tenor" will not serve the kid well.
I am a very logical person and your comment states that you should not let a coach play with your son's mechanics until such changes are signed off on the kid's end (where in the subject case could only be accomplished through some third party instructor). If you said something along the lines of "utilizing video to understand current and recommended mechanics", I would not have said a word. When you strongly recommend that the coach should be doubted until such time as you choose not to, then I do have a problem as that approach will get kids kicked out of programs.
PS - could not help but point out language usage "facts" and "rash". In much of baseball, there are no hard and fast "facts" and coaches are seldom "rash".