First let me say that I am my sons biggest advocate. I am also his harshest critic. When he complains about who is playing where I simply tell him you want the spot then go take it from him, knock him on his arse, beat him off the ball, when coach says I need someone to do just hustle to him and say I got it coach. He seems to think that being on the Scout Squad is a bad thing. I disagree 100% you blow up my O or D on the scout squad I want to know why your not on the other side because someone on the starting side aint cutting the mustard!!!
I tell all of the parents and kids that preseason practice is where you get to show me what you can do and how much you have in the firebox. Coaches determine who plays where based on that performance and needs of the TEAM. I have literally taken Dads on the practice field and shown them Little Billy isn't quite there yet, to no avail. You can tell them and show them, it doesn't make a difference. In their mind Little Billy is the next coming of Payton, Butkus, or Unitas.
Sadly if they become a distraction or a source of drama for the team or other parents, its best to tell Billy's parents to keep him at home as they are not welcome any longer.
You want my whistle you can have it! If you better prepared than I am and have the experience to lead the team to better place, I will indeed stand aside and cheer you on. However, since you are standing here advocating something that I haven't seen from your son in X number of practices and Y number of games, I'm fairly certain the aforementioned isn't the case.