With regard to teaching children sportsmanship, I believe it was the tennis player Bjorn Borg who recounted that, as a child, he had a terrible temper and would slam his racket and carry on whenever things didn't go his way. His parents took away his tennis racket and told him he could play again when he demonstrated some sportsmanship. That solved the problem in a hurry.
Yes, I coached soccer in an SF Bay Area high school for ten years. We would have gone to the coach of a team with unsportsmanlike players after the game and expected to see issues resolved by the following year. As far as unsportsmanlike play, the refs have the yellow and red cards for this, and an important aspect of the game is being taught when these cards are used.
If I personally saw unsportsmanlike play or post play on the part of my players, they would find that this was not an acceptable aspect of the sport, or they would have been gone.