proctective dog

Question
My dog is a boarder collie mix and is very smart. He hates certain people who have been mean to him in the past and all ways remembers them. He seems to hold a grudge and will pay them back for all the teasing and kicking and water squirting and what ever else they do to this dog.
Is this normal for a dog to be this smart. I think it is. I treat him just like anyone I know and he seems to understand most of it. I just pulled him off a friends of my son who he does not like. He had him pinned to the floor. What do you think?

Answer
It appears that you are allowing your dog to be subjected to abuse by various people, including other people's children, from whom he should be protected at all times.  I don't understand the purpose for allowing other people, with whom the dog does not live, to in any way "be mean" to him.  I think that, in future, if your dog takes the next step in self defense by biting your friend's son, you will be sued, and the dog will be confiscated by animal control and euthanized.

You need to protect your dog from your abusive friends by containing him when they are in your home, so they no longer have the opportunity to subject him to their bizarre behavior.  I also think you need to understand the raison d'etre for the Border Collie, which is designed to be a herding dog, one who should work closely with its human partner.  Your dog needs a job.  Clicker train him and teach him some obedience tricks.  Make him earn his keep by "working" for you, and get some large beach balls so he can work off his herding instinct in the back yard under your supervision by controlling them.