So depending which numbers you believe, somewhere around 50% of children get bitten by dogs at some point.

I'm not sure what other animals attack humans with that regularity, but it makes a certain amount of sense to be scared of dogs.

I'm sure pit bulls (or any breed of dog) can be perfectly friendly. Unless abused, or startled, or feeling threatened, or you know, having a bad day (illness can increase aggression). There's a lot of reasons a dog can snap, bite or full out attack. Judging the temperament a strange dog, especially for people who don't have the opportunity or inclination to get to know a variety of different dogs, is difficult.

Pit bulls (and other breeds of fighting/attack/guard dogs) may not be inherently more aggressive than any other breeds, but they happen to be equipped with the tools to make attacks that much more serious/deadly when they occur.

As a parent of a toddler, when I see an unleashed dog in a park, I try to stand between the dog and my child unless I can talk to/assess the owner and then approach the dog first myself.

The way I see it, dog owners (as a group) have inflicted that loss in freedom on everyone else. I can't be comfortable letting my daughter run and explore in my neighborhood park uninhibited, because I know I'd hate myself if she got bitten by a dog.

There's plenty of dog owners out there who are responsible, keep their dogs leashed in public places, clean up after them, and even make sure they're muzzled if they have any tendency towards snapping/biting etc. I rarely hear of those people approaching the less considerate dog owners and setting them straight though.

Breed specific 'hatred' of dogs is essentially doggy racism. While not nearly as serious as actual racism, it's still being prejudicial against an individual animal based on your preconceptions. That being said, certain breeds attract a disproportionate percentage of irresponsible, cretinous owners, which is unfortunate for the dogs on several levels.