It's sort of self-fulfilling, unfortunately. A lot of people who own them have pitbulls because of the dog's stereotype and, being terrible owners, end up with a potentially dangerous dog that is poorly trained. This just makes more people fear them more.
Is it warranted? I think it is. The last time one of these threads came up a few months back I actually went and paid for a freedom of information request here in Edmonton on dog attack statistics. The city has a relatively strict dog registration policy and rather than most of the stats floating around that rely on media reports that are always 'a pitbull-like animal,' people would be, if anything, less likely to report their animal as a pitbull on official documentation.
I can post detailed stats if anyone is interested but in the past five years there were about 3500 reported dog attacks here in Edmonton (population ~1M). 370 were severe, with 108 from American Staffordshire Terriers. And yes I realize that there may just be more pitbulls here, so I also pulled overall animal registration numbers. 16.5% of pitbulls were involved in an attack consisting of multiple, severe bites. German Shepherds were involved in half as many attacks in five years (50 serious attacks) but that accounted for only 1% of that breed.
Most dangerous breed, interestingly, was just plain old Shepherd, or what people decided to register as such, followed by large mixed breed and then Cane Corso, Mastiff and Afghan Hound. Pitbulls tended to dominate the more serious attacks.
Also, someone reported a chihuahua attack at one point. A level 1 - dog barks, snarls, lunges, no teeth contact. I bet that person was terrified.
