Staffies are lovely dogs, incredible softies for the vast majority. But they have a problem with "Idiot Human Syndrome".
They look a bit like a Pitbull, which means that:
A: Idiots that want an aggressive looking dog, get a Staffie, give it a studded collar, show it aggression, and reward any aggression it does shows - these are bad owners, and they tend to gravitate to Staffies at the moment (now they can't gravitate towards Pitties)...
B: Other humans can be a bit scared of them as first instinct, and avoid socialising with them (making harder for non-idiot Staffie owners to socialise the dog), and have a bias that they'll consider confirmed by a single anecdote.
C*: Having a lot of irresponsible owners leads to being a lot of them in animal shelters, and they take a long time to shift - meaning that there are even more unloved and unsocialised Staffies out there. Also further "confirming" bias against them by otherwise reasonable dog-people ("If they were easy dogs, there wouldn't be so many in shelters")
* Same goes for Lurcher types, which "everyone knows are hard work"