I have even been told by a cop that if my dog were instigated by another breed, my dog would be put down, because he's half pit, and violent by nature, no questions asked.
When bully breeds are homeless or found and taken to shelters, most shelters just put them down, because they'll have a harder time finding a home for a bully breed, than some other breed/mutt, because the majority of people looking to own a dog won't adopt a bully breed because of their reputation
They have a bad rep, because there are idiots out there who don't know how to own a dog. Instead, they abuse them and train them to fight to kill, and the whole breed gets a bad rep.