Occam's Razor: They are known for being more dangerous because they are more dangerous.
EDIT: So. Many. Downvotes. But not a single comment refuting the statistics with facts and evidence... You're not flat-earthers, right? So don't act like them. Use your brain, not your feeeelings! I love dogs. All dogs. And yeah, if my dog was a Pittie, I would be defensive too, but I would also be honest that people need to take extra precautions...
How do you know you have a weak argument? You post "evidence" that has no relevance to the discussion because you're so focused on your feeeelings you ignore facts and statistics.