Have you ever owned a pit bull?  They are sweet dogs, but they get really big.
Yes, I actually have two American Pit Bull Terriers!
Pit bull
yes, these are the dogs which were used in blood sports, that are now banned
Do you know how much they weigh?
Quite a bit, I suppose. Since they have very strong physical characteristics!
Why were the blood sports banned?
Because they were sports that involved bloodshed, and were cruel to animals. 
What does that have to do with them being banned?
Cruelty to animals
Cruelty to animals, also called animal abuse, animal neglect or animal cruelty, is the infliction by omission (animal neglect) or by commission by humans of suffering or harm upon any non-human. More narrowly, it can be the causing of harm or suffering for specific achievement, such as killing animals for food, for their fur or even their tusks; opinions differ about the extent of cruelty associated with a given method of slaughter. Cruelty to animals sometimes encompasses inflicting harm or suffering as an
Terriers and American Pit Bull Terriers bred to several bulldog-type breeds. It was created with the purpose of being a family companion dog.
While some of the founding kennels, namely Razor's Edge owner Dave Wilson, affirmed that they used only the two first aforementioned breeds to produce the desired dogs, it is consensus that at least five other breeds were used to attain the more "bully" physical traits desired. These are assumed to be the American Bulldog, English Bulldog, Olde English Bulldogge, Staffordshire Bull Terrier