I don't know about the other leagues but Presidio/SDDA has the following "gaming regulation":
"Coaches are expected to coach their teams in a positive and respectful manner. Presidio/SDDA Soccer League encourages referees to discipline any coach for irresponsible behavior if the coach...uses derogatory words or actions aimed at their players...."
My son played SCDSL this year but in the 4 prior years of SDDA I never once saw a ref discipline a coach for derogatory actions towards his players despite there being plenty of opportunities to do so. I don't doubt that there are a few refs out there that would, but my I guess is that most refs either aren't aware of their authority to do so, or don't have the confidence to do so. Ironically, many refs are quick to confront a coach if the derogatory words are directed at them. Call me idealistic but I think the same standard should apply whether the derogatory words are directed at a ref or a player. I could even make a good faith argument that they should be even tougher on derogatory comments to kids, since it involves an adult authority figure to child communication versus ref and coach communication which is typically adult to adult. Obviously those types of comments are inappropriate regardless.
Coaches that use intimidation and fear to "motivate" are lazy and uncreative. They typically are the same coaches that joystick their players throughout the game. I'm all for passionate and demanding coaches, particularly when it comes to effort; however, I draw the line at intimidation, condescension, and belittling comments. That type of coaching, at best, only yields short term results, and at worst destroys a kid's passion for soccer.