From the 2002 MLB Umpire Manual:
A pitcher must step directly toward a base before throwing or feinting to that base, but he is not required to throw (except to first base only) because he steps.
Despite what The BRD states about NCAA, under all major sets of rules
any move made from the pitching rubber by the pitcher to a base must be preceded by a legal step. Even with a jump turn, the step must accompany the move and be made before the throw or feint.
This was a balk, and you correctly called it.
YOU CALLED THE BALK, not the defense.
There's nothing wrong in taking your time to assure that your call---although later than the defensive yells---is the accurate call. When the defense calls it, it means nothing. When YOU call it,
it means something.
Don't allow the coach to take the cheap shot by
yelling an accusation that you allowed the defense to call the balk. That is personally attacking you, and you need to let him know you consider it as such. Take control of the game by providing him the warning that those comments are considered personal and will no longer be tolerated. If he says it to you quietly in discussion instead of yelling it, be less harsh with your warning, but let him know YOU called the balk, and you took your time to get it right.
It's better to be slow and accurate versus fast and inaccurate..............
Just my opinion,
Freix