To me the solution to sideline confrontations in youth games (parent v parent and parent v ref) is easy. Team and its parents on one sideline and opposing team and parents on other sideline with parents to the left of midfield. The benefits are:
1) No direct contact between AR and parents
2) Reduces contact between opposing parents and sideline sitting disputes
3) Coach has more direct control over parents behavior (which is coach's, not ref's, responsibility, although some refs prefer to engage directly with parents). This, of course, assumes coach isn't also crazy.
4) Reduces coaching by parents as coach is more likely to hear parents on same sideline (I've noticed significantly more parent coaching when parents are on opposite sideline)
Yes, parents should just behave themselves. But the reality is that its not happening. We had a friendly scrimmage (ECNL and DA B07) the other day without a ref and very little coach involvement. The players policed themselves and played freely, it was a refreshing and fun to watch kids play in this environment. Of course, one jackass parent had to ref and coach from the stands the entire time.