As some people are crazy, some animals are also. Some breeds tend to produce more of vicious dogs than others because of inbreeding, others breeds the inbreeding causes other problem such as joint problems in English Bulldogs.
Unless you can present some factual stats that are relational across all breeds, I won't accept the concept of Dobes or bulldogs are any more prone to producing nutcase dogs.
Pitbulls get press because of their large numbers and lack of training in the urban areas. Dobermans get bad press for their portrayal in movies and hollywood. The only bad dobes that I have seen are chained up dogs with zero training.
Every breed has their pack of bad seeds and its NOT more abundant in certain breeds than others. I just dont see any reason to believe that.
If thats the case, explain muts.