Understanding Balks in Baseball: Rules and Umpires' Discretion

Question
When a balk is called against a pitcher.Why can't the
manager argue against it?

Answer
Sorry for delay...I have had no internet for several days.

The idea of a balk is that the pitcher has unfairly fooled a runner by beginning a pitch, but then interrupting that action (usually to try to pick off a runner or stop him from leading or stealing.)  It is a tricky rule, and it is the umpire's judgement whether or not there was an illegal move.  If so, the ump will move the runners ahead one base.

Here is a more detailed explanation I found on Wikipedia:

http://en.wikipedia.org/wiki/Balk