Consider the following. I recently heard from a Referee Assignor that the attrition rate among young referees (minors) is about 50 percent. These young people get their Grade 8's and after about 1 season of serving as an AR or Ref at the club soccer level, drop out, never to be heard from again. The 1st reason is A-Hole parents; the second reason is A-Hole coaches; the 3rd reason is A-Hole parents (see 1).
We have a problem. Grown men and women think is cool to demean and degrade the kids in yellow doing the best job they can. Sure, they get $31 for spending 140 minutes doing the best job they can and they do make mistakes.
A stadium setting is much different than an intimate sideline setting. In the stadium the words are nothing more than background noise versus cutting like a knife in that U14 game hearing from the A-Hole Dad 10 feet away. That 45 year old can take it and brush it off as the ramblings of an idiot (and laugh about it like I do), but that 13 or 15 year old AR is going to take it to heart. They will run that sideline and finish the game and may leave that day and never come back.
Respect. Its a word that some understand and some don't. You can respect something without agreeing with it. All we ask as parents, coaches and refs is Respect the game. Respect the players. Respect the referees. If a parent feels the need to disagree, at least be good natured and cool about it. Its youth soccer after all.