How does the umpire keep control of the players?

Answer 1

Rule 9.01d states very clearly that "Each umpire has authority to disqualify any player, coach, manager or substitute for objecting to decisions or for unsportsmanlike conduct or language, and to eject such disqualified person from the playing field." In other words, any umpire, at any time, can simply expel any player acting in an unsportsmanlike manner - and it's ENTIRELY in the opinion of the umpire. It's hard to lose an argument when you can simply tell somebody they've just lost the argument and have to leave immediately!

In addition, players who so much as touch an umpire with their finger are invariably subject to very severe penalties by Baseball commisioners.