Its true that the bad behaviour at the top of the football pyramid sets the tone. I have a couple of players in my u10 side who regularly watch premier league and unsurprisingly, they are the ones who I have to remind about how we play the game. One asked me if he could dive in the penalty area the other week because we were losing (I told him he could, but he would be substituted before he hit the ground...).
It seems very simple to fix too, just have a sin-bin and use it. IMO it wouldn't take many episodes of players sat next to their angry manager as they're a couple of players down for 10 minutes, before they start thinking about it. I have a mate who reckons that'll never happen, because football is a world game, and some parts of the world see gamesmanship and seeing how far you can push the rules as a the best part of the game. I dunno if that's true or not!
On your issue Phil, take your point about youth refs not much older than the players, but I think it also sounds largely down to the opposition coaches. Sounds like they have forgotten why they got in to youth football in the first place, and just want to win regardless. Sad state of affairs. If my team were bullying the opposition, I'd be whipping them off the pitch for a serious conversation in droves.