I never believed in one breed being particularly violent but 7 years ago, my neighbor's pitbull ran into my front yard as I was walking my dog (who was the same size as the pit) to my car, and he grabbed my dog by the throat and threw him to the ground, thrashing him about, my dog yelping frantically. I was paralyzed. I just stood there, screaming at the top of my lungs. I knew if tried to break them up, the pit would go for ME and if I didn't...my dog would be killed. My neighbor finally appeared and threw himself on the dog, dragging him away by his back legs.
My dog was mauled - the vet said he would've been killed if his hair wasn't so thick. He had to be treated with intravenous antibiotics and get stitches in his face and neck. His skin (visible after the vet shaved him) was purple everywhere and his eye socket and lip bulged out so profoundly, he couldn't eat or drink normally for days.
$300+ vet bill. My neighbor refused to pay it. I called the police - they gave him a citation. The guy never paid it, and the police would not follow up with him. (I called them three times.) The dog continued to ram our shared fence over the months that I lived there, knocking down the pickets trying to get to my dog until I finally put screws in them all.
Needless to say, I was traumatized by that experience. Even now, all these years later, I don't care what the breed is, when a dog runs at me barking, I panic. And I won't go near a pitbull under ANY circumstance.