You can see it in their eyes.
My neighbor has pits (in kennels, in their living room)
They drove way out to western SD to get a bull terrier/pit mix off a reservation that was tied to a tree and left for dead.
I stopped over at their place to borrow a tool and they brought him out and said how nice he was. I was stroking him between the eyes during our conversation and he was wagging his tail.
I looked down at him and his eyes went from brownish to pure black. I told the neighbor "Get him away. He's going to bite" The neighbor said "haha no he won't, he's nice"
I pulled my hand as quickly as he went for it and only ended up with scraped fingers. Little blood.
My point is, no matter how much you think these dogs are good, you never know when there will be a fire in the attic.
Reminds me of my Chinese sister in law who was certain that my Doberman (an absolutely friendly dog) was aggressive and would attack her, based on her understanding of the breed. One day, afraid of my Doberman, she arrived for a visit and slowly creeped open the door from the garage leading to the laundry room. My Doberman watched this with pricked ears and on full alert. Then, very quietly and slowly, she poked only the top of her head past the edge of the door to peer inside, just up to where one eye passed the edge. My dog immediately detected that someone with ill intentions was sneaking into the house and charged toward the door, barking and snarling. She quickly pulled back and slammed the door closed. She then concluded that this was proof he was no good and that she was right about the breed.
Act weird, scared, and suspicious around most dogs and, unless the dog already knows you, you should expect an aggressive reaction of some kind. In fact, that's how agitators behave around dogs they're assisting in training for protection work. It's designed to rouse the initial aggressive reaction towards suspiciously behaving people (followed by the agitator running away in apparent terror of the dog), which aggressive reaction is then praised by the handler as though the dog was the hero who saved the day.
Your prejudgement of the dog, based on breed, caused a fear reaction in you, followed by suspicious behavior picked up on by the dog. Based on this, you should limit yourself to interactions with only the softest of breeds.
