When the occupants of a player’s bench show violent disapproval of an umpire’s decision, the umpire shall first give warning that such disapproval shall cease. If such action continues—
PENALTY: The umpire shall order the offenders from the bench to the club house. If he is unable to detect the offender, or offenders, he may clear the bench of all substitute players. The manager of the offending team shall have the privilege of recalling to the playing field only those players needed for substitution in the game.
A stern warning to the manager should always precede clearing the bench. Generally the starting lineup, trainer, and coaches are allowed to remain on the bench, unless the situation deems otherwise. [BRD]
During the 1935 World Series, umpire George Moriarty warned Chicago Cubs players about taunting the Detroit Tigers' Hank Greenberg with anti-Semitic slurs. When they refused, Moriarty cleared the Cubs bench. Moriarty was disciplined for this action by baseball commissioner Kenesaw Mountain Landis.
Players are not "ejected" under this rule. Individual players may also be ejected, but bench players banished to the clubhouse are still eligible to play in the game.