Yeah, dogs, even relatively small dogs, can cause very severe damage very quickly. There's a reason that for a long, long time a dog that bit someone was immediately put down (rabies was also a factor). Even relatively small dogs can cause severe injury resulting in permanent disability. I really wonder if people realize how bad a dog attack can be and how quickly it can happen. Aggressive, reactive dogs aren't an embarrassment, they're a loaded gun and the owner has the safety off and the finger on the trigger. Muzzles should be the norm for any dog that's even remotely reactive when they're in public.

A big factor is; Most people can't meaningfully fight a dog. Many, probably most, dogs are big wimps who have no interest in a real fight. A dog that does decide it wants to fight, though, it's a small target, their heads are narrow, their organs are all under their body protected by ribs, they're very nimble. If you land a punch on a dog it probably won't do much, but if a dog bites, latches, and tears it's going to cause you immediate severe injury.

Again, most dogs aren't going to fight anyone in any circumstances. Even if they bite someone when they're cornered and scared they're just going to nip and retreat. But a dog that does commit to an attack is extremely dangerous, and the danger increased the smaller, younger, or older the victim is.