You're absolutely correct. Any dog over about 10kg has the power to cause serious injury, especially to a child or other dog/pet. Greyhounds have a horrendous prey drive and will eat your cat in 2 seconds flat
I tried to rehabilitate a dangerous dog and failed and now find myself with another one (thankfully MUCH less prone to biting). "regular" dogs are one abusive/neglectful adolescence away from being unsafe
Pitbulls, Staffordshire terriers, Bullies etc, are all variations of same or similar breeds. These breeds are viewed as 'tough' and are treated and trained as such by their owners. They also aren't treated like family dogs by these people who buy them for their tough image either.
You get a few generations like this, a couple idiots who don't desex or seperate their dogs on heat and you've got the beginning of a problem.
I'm Australian and in animal control, bull breeds are always number 1 for attacks every year but working breeds are VERY close behind, think Cattledog, Kelpie, German Shepherd etc.
If you look at the skewed breed ownership statistics, there Staffys and Bull breeds get a bad wrap from being incredibly popular and very poorly taken care of.