So, if a player hasn't questioned any calls, has been polite to his opponents, and "has behaved so far in the game," you wouldn't call a technical foul on him for slapping the ball while the thrower had it OOB for a throw-in?

This situation is no different. The T is not for disresepctful behavior. It's for interferring with the play and preventing B from advancing the ball up the floor.

If you don't T Coach A, you'd better realize that you're probably going to have to T Coach B. :(