The usually call it "little dog syndrome" when little dogs act like they are giant dogs in tiny bodies...

Breeds can sometimes make a dog, as in, some breeds have a very different personality than another breed of dog. But no breeds have been bred to show aggression towards people, unless trained to be an attack dog, but that is training for a specific job, they aren't people aggressiev all the time. Chow chows are one of the few breeds that were bred to be aggressive towards dogs, but they never stopped them from being aggressive towards people, which causes problems, but I've met plently of nice chow chow's before.

Same goes for other breeds, mastiffs and great pyrenees are known to be more stubborn then let's say, a border collie, which love to learn and please their leaders.(owners)