Some points:

1) Pit Bull is not a breed but an umbrella term for a number of stocky dogs used for fighting originally then used for: hunting, farming, and as 'nanny' dogs

2) They are some of the most over-bred dogs in America(along with Rottweilers) and this, as well as the popularity of them as 'manly' dogs among less privileged socioeconomic classes, contributes to the prevalence of the idea of these dogs as particularly aggressive.

https://www.thedodo.com/people-are-breeding-pit-bulls-over-a...

http://saveabullmn.org/pit-bulls-and-euthanasia-rates/

3)Breed is arguably a poor indicator of risk.

https://en.wikipedia.org/wiki/Pit_bull#Dog_attack_risk

4) They have been found to be no more human aggressive than other breeds though they trend towards dog aggression.

http://www.akc.org/dog-breeds/american-staffordshire-terrier...

http://journaltimes.com/news/local/defending-the-pit-bull-ex...

https://www.aspca.org/about-us/aspca-policy-and-position-sta...

Specific dog breeds do tend to exhibit behaviours naturally associated with that breed but if you're going to own a dog, look after it. That's all. Making generalisations about breeds needn't override that.

Training goes a long way. Yet my experience with dogs is that there are individuals with a bad temperament. And breed does strongly correlate with size. So in situations where a bad mannered individual dog of a large breed does act out the potential for harm is higher than if it were a smaller breed.

Owning large and powerful dogs of any breed is a risk.

> Owning large and powerful dogs of any breed is a risk.

Pitbulls aside, anecdotally, if we're talking breed size I've found Pomeranians and Jack Russells to pose more danger than, say, collies, labs, Great Danes, Newfies, etc. but I guess now I'm the one generalising.

I think training and care are really the main factors. There are certainly cultural tendencies to apply certain training approaches to certain breeds, but I really do think this is mostly correlatory.