Lots of dogs can pose a bite risk but pit bulls pose a rather unique mauling risk. It's not just a bite but a frenzied attack that doesn't stop until someone is dead. This is what the dogs were bred for and it's what we get almost uniquely from the breed.
It's not just because they'd big and strong... lots of breeds and big and could kill if they attacked relentlessly, but even when agitated and angry it almost never happens, except for pit bulls. They pose a unique risk for viscous attacks.
Some breeds are genuinely extremely aggressive. I'm not usually bothered by dogs, but on a holiday in the canary islands I felt genuinely unsafe because of the local breed of asshole dogs.
My wife was home sick one day and I started to feel sick so I left work early. For some reason I don't remember why I came in the house through the front door, when I normally came through the garage. Upon hearing the front door open at a random time of the day and being very protective of us especially when sick, my borde collie came running out of the bedroom growling like I had never heard her do before with teeth showing. The second she realized it was me she stopped and came over for pets.
There is one right point though, this is mostly stupidity of humans who think that buying a pitbull will make their penis larger. Its owner should be jailed on three independent accounts of man and child slaughter