It is a great thing for your DD to learn that not every coach is very good or has something worthwhile to teach her. Sometimes she can learn a lot about what not to do from people. What this coach said was careless and shows that he doesn't understand how to coach and motivate kids. He certainly does not understand the sometimes frustrating process of developing a slapper. She needs those moments of success to fuel her confidence when she has been struggling with slapping. Good luck to your DD!
I understand the comments - but these kind of comments also drive me nuts. How long is long enough to take this crap before stepping in as a parent? What would this a-hole have to do or say to get you to remove your DD from this toxic situation? Just curious.