My suggestion - forget the last two classes. Why put yourself through this trainers personal criticism and get yourself all discouraged. Don't give up on classes though. Find another trainer who will work with you. You can find one. May I also suggest before doing class work that you find a behaviorist in your area who can really diagnose your dog for tendencies of aggression. It doesn't sound like this dog is a killer by any means. He just needs the right beginning and a good behaviorist can make all the difference.

Hang in their and give that pup lots of loves and kisses. Everything will work out fine in the long run.