I tell my parents I have 3 rules before each season begins
1. You are not to say anything to the refs, I will talk to them on questionable calls
2. no comments to the other team or their parents unless something positive
3. be loud and be proud your kid has earned it

I am sorry but the silent thing is one of the strangest things I have ever heard. This is not a chess match it is a competitive sport, it's physical, it's mental and just like everything else in life not every person can do it. I have attended games that seemed more like funerals than they did sporting events. The kids on my team work hard every practice and game because it's expected by my assistant coach and I, they deserve someone cheering for them, they deserve a pat on the back from their coaches and parents no matter what the outcome, that is just part of athletics.