With Emmee being just a year old, I'm very careful with her rough-housing. I try to keep her focused on a toy to play tug of war with, but never allow her to get "pawsy" or to play bite on me. Something you could try...next time he is trying to get another dog to play, put him down on his side in a submissive position, and let the other dog come and stand over him...keep him in a submissive position until the other dog is no longer interested. It's something to think about. And as for the first trainer...I would have done the same thing, but I would have been a whole lot more verbal about the situation
...I have never agreed with prong collars, I feel they can be mentally damaging...but that is just my opinion.
Good Luck!!!
Heather