Its been a habit of football managers to insult the on-field referees. It is really bad for the game in general. I won't say that the referees don't make decisions that normally favor top clubs.
It is about protecting the interest of the game.
The classic example can be that of the former Chelsea coach Jose Mourinho condemning a referee for poor decisions. The referee got life threatening calls from fans and quit the jobs. Like us even he is human. He doesn't have a television set where he can watch replays over and over again. Referees have to make decisions at lightning speeds.
The managers should know they are responsible for everything they do off and on the field. They should act as professionals, it's about time.
When a manger is found guilty of misconduct, he is just fined or at the most banned for two or three games, which hardly matters. The same managers are not learning from their mistakes which is a pity as they are grown up men. One should always respect authority and on the field always respect the referee. If we wont' teach that to a manager, how can we expect that from a player?