Unfortunately,I have encountered a few mean ,nasty bassets,formed usually, but not always, by the owner. It can happen when an owner does not know how to deal with a dog that starts to develop aggressive tendencies as a puppy and the owner allows them to get away with or intimadate. There can be an inherited side to aggressiveness as well. So poor breeding can leave its mark too. But for the most part Bassets are exactly as you have described.