There was a TV program called pit bulls and parolees. This woman ran a pit bull rescue. That question came up one day and she said that is NOT true. A lot of people breed them for particular characteristics such as color with no consideration for other characteristics such as temperament. She believes some dogs are just born not quite right and that some are not adoptable. She had dogs she would not adopt out, period.
Personally I wouldn’t adopt any of them out.
I knew a couple who loved dogs and raised many of them. At one point, they had two dogs and adopted a third dog - a pit bull. They said it was very aggressive, and suddenly their other dogs started giving them worried looks. The couple ended up having the pit bull put down. These were people who really, really loved dogs, so they must’ve had a good reason to do that.