There is a huge difference between pitbull type and Mollosor type dogs.
The statement that it's in their nature can be true to some extent.
Some of the Mollosor breeds can be and are dangerous dogs to own,I can think of atleast 3 breeds that even judges at rarebreed dog shows wont put their hands on. These dog have been bred for years to be human aggressive and thats the difference between them and "pitbull types".Oh and of course the size difference to.
If your interested in read or finding out about 1 of these dogs look up a Fila de Brazilia{sp} some reach 200lbs and close to 38 inches tall.They look like an over grown bloodhound but make no mistake this dog is anything but a laid back bloodhound.
Pressa's that we see today are a resurrected breed and have been bred to encourage that human aggressiveness.
A local breeder had to unlist their phone and pull all adds they had after the story of the woman being killed,their phone wrang off the hook with people wanting 1 of their dogs.
They do their best to see all dogs are placed in experenced homes and cut back the breeding program,all because of "idiots at the wrong end of the leash.
Then to make matters worse,they ban a 35lb staffy but let any fool have a 140lb+ mastif.....