[wolfy dog]

Neutering will not fix his adolescent brattiness. Your son domineered him while he didn't have any business doing so. This is is according to your dog who is growing up and starting to assert himself since no one else has taken that on yet. A lower in rank dog cannot stand over or "hug" a higher in rank dog and will be punished if he is stupid enough to do something like that. If you punish him in the presence of your son, he will avoid him, but it will make it worse. You are lucky that he growled and didn't attack. It doesn't sound odd at all to me but of course it need to be addressed. Neutering a large male at this young age can have negative effects on his bone structure. I bet that it is a training issue.