In a movie Lagaan, there was a cricket match going on between the ruling British Empire and the native Indians. In that match, a very important bowl (from the view point of both of the teams) was decided to be a "no ball" by the umpire. Then the fielding side i.e. the British team's captain angrily went to the umpire and demanded the decision to be reviewed. But as in cricket the umpire's decision is final and he does not stand to clarify his position to anybody, the umpire refused to discuss it with the captain and replied (somewhat diplomatically)
I am not discussing it.
It seemed to me the statement means "I am not going to discuss it with you". Is that correct? If it is, then are such constructs used in cases to bypass any question or hide some emotion (in this case the fear of being caught or to sit for a debate)?