Have you experienced having a vicious pet? We had a pigeon that we named Twinkle who stayed with us for more than 5 years. She was living inside the house and only comes out once in a while to peck on dirt (which she needed for her digestive system). Since she stays inside the house, her toilet is the living room. We had to pick up her poop which she excretes about 5 to 10 times in a day. Her favorite is the sofa fronting the tv so we had to cover that sofa with a blanket. However we tried to teach her toilet manners, she doesn't obey albeit she pecks us with her beak that is painful.
Twinkle is so vicious that even our dogs were afraid of her. Sometimes Barbie would threaten her and Twinkle would get back at Barbie by pecking on her head so Barbie would run away. It's difficult to have a vicious pet like Twinkle because we cannot implement law and order in the house.
The only pet I had that was vicious was an adopted dog that we temporarily had. We tried very hard to keep the dog because it was a foster dog and figured it just needed to learn to trust us. But after a couple months it would still jump up and attack us with full teeth and claws. Mom had to send the dog back because she didn't think it was safe for us to keep.
Other than that I firmly believe domesticated animals are as nice as their owner's let them be. So vicious pets are a reflection of the previous or current owner. I once had to babysit some kids with a vicious dog. They couldn't even play in their backyard because the dog would chase them around the house and pin them to the ground. He was the father's hunting dog, and was great for protecting him from cougars and coyotes but not really a family pet. I also think there is a huge distinction between vicious pets and protective ones. There are guard dogs that are trained not to let strangers in the house or on a property and I don't consider them vicious, even though they can be.
If a person has an animal that is considered a pet, then that animal should never be a vicious one, especially a large dog. Not only can it be dangerous for the family that owns the pet (especially when they have children); but if the dog bites another person, the people wold probably sue the pet owners, and they would have to pay expensive medical costs.
Also, there is a law, at least here in the United States, that if a dog or cat bites a person, the person has to be tested for possible rabies, and the animal is usually put down as a dangerous dog, or because they might have rabies.
Sometimes, farms or even businesses will have a guard dog, and then that dog is not supposed to be a pet, and when the business is closed and the dog is on duty, it is part of his job to stop an intruder, even if he has to bite the person to do that.
If a dog is protecting his owner, and bites someone, then the dog is only doing what he is supposed to do; so normally that would be fine and acceptable behavior, even if the dog was a pet.
As for the pet pigeon that pecked people, I think that I would have moved it outside and kept it out there ! !
First of all, I've never heard of someone keeping a pet pigeon in the house. Pigeons belong in coops in the backyard. Birds are basically incontinent, and poop wherever they happen to be when the need arises. Some birds will poop as often as every 15 minutes, so I can imagine the mess when a bird is allowed free roam of a house where people live. I used to have several pet birds and they were never allowed to remain outside their cages for long and would always return to those cages when they needed to go.
Secondly, as far as vicious pets are concerned, yes, they happen sometimes. I think many times the pet in question just likes to play rough. My cat is like that. She plays using all of her weapons, including teeth and claws and even vocalizes while playing. (hissing, growling) She has incredibly fast reflexes and can swing her paw away from me and in the next second swat me on the hand with it faster than I can blink. I can tell by her facial expressions, and by her tail movements whether she's actually angry or not.
Also, some pets like to try to be dominant. My cat is also an example of this. She has an alpha cat personality, and does think she is head and shoulders above the humans in her 'care'. She absolutely believes that she deserves the prime spot on the bed at night and anyone who thinks otherwise gets a hard bite on the offending limb that stretches into 'her' space. I've been known to simply shove her to one side, which means she has to get up and leave the room as that sort of thing can't be tolerated.
I've never had a pet who was vicious just to be vicious. There was always a reason for it, such as previous abuse, or sensory overload of some kind. And of course, there is the 'Queen of the Universe' that I currently live with. She has some interesting catitude.