Adjusting other parents’ expectations

Can anyone offer scripting for helping other parents adjust their expectations about my child?

My 10M has been diagnosed and on meds since age 4. Same exact story with my 7M. We’ve had experiences with coaches who ostracize, come down harshly on, or otherwise unduly discriminate on our older son. I’ve been volunteering as a coach because I wanted to be there to support him; today, one of the other coaches pulled my son out of the group and made him stand alone as a punishment for being silly with his friends. This is community baseball, and this coach is also his scouting leader, so he has to interact with this guy a lot. This guy has told me a few times that he “lacks empathy” and seems to believe in a tough love approach. I sincerely think that he believes he’ll somehow break my kid of his ADHD if he yells at him hard enough.

How do you educate other parents about how to respond to your child effectively? How do you stop yourself from reacting with anger and creating a scene? My son tells me that he’s never doing scouts or baseball again, and I can’t say I blame him. His self-talk is becoming an issue, poor fella.