Do you have 'Hassle Opponents' on? If so, remove that;; Also, maybe try telling them to calm the **** down during team talks;; Also, go to the player who has received the Red, go to Ambassadorial Duties in Private Chat, and talk to them about the suspensions. I forgot which of the three statements were effective, but it varies depending on managerial reputation and the like.
Maybe that helps to some extent..