Competition is an important part of learning and development.  Players don't get better without competition.  It's what drives them.  But allowing competition to cross a line into a toxic learning environment where players are stressed out and afraid to make a mistake or perform poorly at practice won't help them improve.  It will stunt their development and maybe even drive them out of the great sport of soccer.  The adults are key here.  Parents and coaches need to be on the same page, communicate with and support one another, for the players.  Because it's not about the adults.