@CastorTroy Then he really messed up somewhere along the way. There are bad or mislead owners, even with the best of intentions.
Especially if you have one of the strong large intelligent breeds, you have to be alpha, calm, stable and confident leader. Otherwise the dog will lead YOU. Sounds like your neighbour is the Beta here. And that is very BAD for everyone involved. Because an unbalanced dog has erratic energy and behavior. Exercise, discipline and love, in that order.