That is it in a nutshell really. There is no such thing as an inherently bad dog, there are unsocialised and untrained dogs.
My daughter's dog is a border collie/lab cross, and a more affectionate beast you would never meet. He doesn't just wag his tail, he wags his whole rear end
. He is big, probably about 40 kilos, and it is all muscle, but he has been trained properly. She takes him to the park at 06:30 every day, where he meets his friends, and they chase each other to exhaustion. The other morning he was playing chase with a fox, he chased the fox, the fox chased him.