"Whats wrong with growling?
Did you seriously just say that
Maybe you missed the bit that said it then attempted to bite my son"
Nope, I didn't miss that bit.
Dogs growl as a way of communication, just like wagging their tails, holding their tails down, pinning their ears back, barking etc. Growling is a way of saying they don't like something or aren't comfortable in a situation, no more, no less.
Are you sggesting dogs have to be happy with every situation we put them in? That they shouldn't let us know if they aren't happy with that?
The dog growled at your child. That suggests to me that the dog either wasn't happy with your child being near to it or what your child was doing at the time. You then allowed your child to continue to be near the dog, presumably without any behaviour modification, since you think dogs shouldn't growl. Did you also tell the dog off for growling? It was your fault and your fault alone the dog was put in a position where it felt it had no option but to bite your son.
The dog in the OP is not 'biting' in the true sense of the word, it is over excited and hasn't learnt that the puppy like behaviour of jumping up and nipping is not acceptable. It needs training and I highly doubt it is dangerous. As the OP has already said, she has already seen an improvement in the dog's behaviour.