Whilst I'm loathe to make generalisations about one breed being safe and another being dangerous, it's undeniable that certain breeds have specifically been bred for aggression over many generations. A large, highly aggressive breed needs much more careful training to prevent it being dangerous than one that is less aggressive.Your basing that on nothing but reputation when you probably haven't researched or owned a dog yourself.
Most people don't train their dogs perfectly, so it's reasonable to have a degree of trepidation about certain breeds.