When it comes to bull-type terriers, they were bred for the less noble purposes of hunting vermin and dog fighting. Yeah, they can be aggressive towards other dogs, but most of the time they go easy on people. That said, any doggos prone to animal aggression likely have had some straggler bulldogs thrown into the mix. That's especially important because we know that animal aggression can translate into human aggression via certain herding dogs, like German Shepherds and Border Collies, which can mistakenly think of humans as their flock. And their in-built instincts push them to take a dominant role that could easily cross over into hostility toward humans. To try and stop that happening, you've got to figure out what's causing the aggression in the first place. Trying to keep things chill and rewarding the animal when it does what it should, is a way of reining in any potential aggressiveness.
A better example; is the Australian Cattle Dog which is ironically rumored to have Bull Terrier in its foundation stock.