Ok, where to start. First, my kid plays and the coach is still an idiot. 
Second, if a parent has an issue with a math teacher being a really bad math teacher, they can and should say something. I uncovered a math teacher using answer keys which where flat out wrong. Should I just stay silent? Who cares if the kids are struggling because their homework answer keys are wrong?
I think it would go a long way for coaches/ADs (and others) to accept the power structure of any public school. It starts with the voters. You have three active communities of voters. 1) Old people. 2) People that don't want their taxes to go up regardless. These two groups show up for tax referendums. 3) Parents of kids in school. This group is engaged while their kids are in school plus/minus a few years. School board members usually win their seats by a handful of votes. So parents matter to them. Once that is accepted, things are easier to manage and you can see where the pressure points are.
Good districts will have good board members who are able to deal appropriately with all sorts of complaints. And little Johnny not playing is just one of many they get every week. Good Boards will hire good people -- and good Principals and good Ad's will provide somewhat of a shield behind which a coach can do his/her job. But what parents and players mostly want is competence. They don't want to pick the team, determine playing time and all of that. The vast majority of programs go along without issue -- most are small, at the margin, and dealt with. A small minority have issues and make the news.
The big thing now is "old school" vs. "new school" coaching. Things have definitely changed in that respect. "Old school" is no longer acceptable - whether that is good or bad is a different conversation. The parents wont accept it -- so they go to the board with the horrible "stories" and the the "old school" coach is gone. Nobody has ever said the coach should be fired because he is too nice.