Certainly a vicious dog can tear off a chunk of flesh, break small bones, and, given a little time or perhaps a pack of dogs, maim and maul to the tune of hundreds of stitches, as well as severing arteries causing blood loss resulting in death. Small children and elderly people are especially vulnerable, as they are physically vulnerable and unable to defend themselves. I had an English Mastiff which could chew up the large joints of a cow like candy. However, a dog cannot tear off an arm, leg, or head as we have all seen happen with bears, sharks, alligators, tigers, and the like. Definitely, though, it has been proven over and over that dogs can kill people, and the smaller the person and larger the dog, the more dangerous the result. I can recall years ago when 3 Pekinese mauled a baby to death.
On the other hand, as the former president of an ADBA-sponsored club here, I once organized and ran an APBT (American Pit Bull Terrier) - only fun show where we had 112 entered dogs without a single incident of any kind. I have offered to lecture on the care, restraint, and handling of dogs here, as we, like most cities, have a big problem, yet I never got any response at all from any dog organizations here. Apparently, they like things to happen first so they can provide a knee-jerk reaction after the fact, or maybe they simply like to appear to know everything.
The gist of my lectures would be the methods and different types of effective restraint of a dog, as well as the bad ideas. For instance, double nylon collars, rather than a single leather collar. Eventually the leather can stretch and the dog gets away because the owner never checks it. And one would be amazed how many people tie up their dogs with rope or light chain, which any self-respecting dog will chew out of immediately. And some people walk or tie up their dogs in harnesses, which some dogs are very adept at backing out of. A dog anywhere in close unavoidable contact with people should be muzzled just as a courtesy.
And it's amazing how many dog owners think it's funny when their dog barks at someone, either off- or on-lead or through or across the fence. Not many people find this amusing. Or how many people will let their dogs loose unrestrained on their property with the result that the dog runs off the property to challenge someone or chase something, then runs back on the property. Also a dog should never be aggressive towards its owner, even when pushed off its food dish. It should never growl at the owner's family, and especially not at children. If it runs off its property and attacks a person or another animal, it should be euthanized. No 2- or 3-strike rule, because the 1st strike could kill or maim a person. And there is liability on the part of the dog owner. The injured person has recourse to civil suits. Sue the pants off the dog owner.
A dog should be trained to stay in a travel kennel when on the road, so it doesn't run out and chase or attack someone or something. The collar should be no looser than 2 fingers between collar and neck, and no tighter than 1 finger. The size of the collar and strength of the lead and clasp should be proportionate to the size of the dog. Double clasps with strong swivels are a good way to prevent a dog from unfastening a single clasp, which some dogs have a knack for doing. Of course, all dogs used in a public setting should have a minimum of training. It only takes 10 - 15 minutes of training per day from an early age, say 4 - 6 weeks, to train a dog.
A dog which attacks its owner, family, or friends without good cause should be euthanized, not taken to the pound or given away where it becomes someone else's problem. And a loose dog or other dog problem should be reported to the proper authorities BEFORE an accident or tragedy. You'd be surprised how fast these bad-assed gangbangers with impressive dogs run and hide under their bed the first time something comes down. Who did you see defending Michael Vick?... not that he deserved any defense. A guy who would electrocute or drown dogs that just fought for their owner should be drowned or electrocuted himself. But his own family and friends rolled over on him and ****ed on themselves to save themselves stiffer charges and potential jail times and fines.
When one's dog of a particular breed attacks someone, it reflects on the whole breed, not just the individual dog or the owner, just as a guy who trains in karate, MMA, or any martial art, then gets busted for rape, child porn, mugging, or drugs, reflects on the whole art. People are fear-mongers. They need to know dogs, and by extension the dog owners, are under control, rather than out to get them. Sorry, I tend to rant on this subject. BTW I see where LA just passed a law requiring most dogs and cats to get spayed or neutered. I think LA will always have a problem until they require the spaying and neutering of most people. As the late great Pete Sparks said, "The more I see of people, the better I like dogs"....