First of all, there is NO "Pit Bull" breed. There are the American Staffordshire Terrier, American Pit Bull Terrier, and the Staffordshire Bull Terrier. These dogs were made up of a cross between the Olde English Bulldog (meaning NOT the super brachycephalic breed that most people see, but its athletic predecessor) and terriers. Hence . . . Bull Terriers. And yes, the eggheaded breed is also a cousin of them, along with Boston Terriers, Great Danes, American Bulldogs, and others. "Pit Bull" is really more of a category.
Also, the APBT and AmStaff standards call for dogs who are 40-60 pounds, so these 80+ pound behemoths that people are breeding now are more than likely crossed with something larger, like Danes or Mastiffs.
My Corgi is more DA (dog aggressive) than the two APBTs I know well. Unfortunately, it's a breed trait for APBTs and AmStaffs to want to have it on with other dogs (the same with Shiba Inu, Akita Inu, Staffordshire Bull Terriers, and others), so it's really to be expected of them. GOOD and KNOWLEDGEABLE Pit Bull owners know this and act accordingly with their dogs. HA or (human aggression) is never to be accepted and all dogs displaying it have historically been culled, but some dumb jerks are perpetuating the behavior and breeding it in in order to make a guard dog out of a dog that has NEVER been meant to guard or just plain to make their dogs mean for their own status gain. It's stupid.
It's funny, because my friend Stephanie has an APBT named Piper and she attends the training school where I just started teaching. I was talking to her at a distance with a decent grip on Hazel (PWC) because of HIS fear-based DA. I was NOT worried at ALL about Piper -- I know her well.
I also fostered an APBT for a time named Zolf. He played a couple of times with my dogs with NO incident, but I only allowed supervised playtime after I had known him for several weeks.
Here's a picture of Kaya my Shiba Inu/GSD mix holding Zolf the APBT down on the ground while Hazel looks on:
Kaya knocked him over several times and Hazel nipped at his heels constantly. Very, VERY tolerant and sweet dog.
Watch the behavior of any dogs you're around. If you see any aggressive red flags go up (teeth showing, barking, lunging, hackles raised, high, fast tail wags, lips pursed, etc) turn around and go the other way. It doesn't matter what breed it is, all dogs are capable of being DA and a large dog is always more capable of tearing up a smaller dog than vice versa.
Pardon me, I hang out with a lot of APBT people even though I don't have one myself. They're one of my favorite breeds aside from Corgis and Spitz-types.