If a animal is vicious and has killed people for no reason, they should be put to sleep. But I think it's fucked to kill an animal when they attacked someone in self defense or because they were provoked or because it was a puppy and it was just playing so it didn't mean to kill the baby.
When an animal kills rather it was for self defense or because it was provoked or because it was just playing, they put it to sleep thinking it can kill again. But yet if a child kills, they sure don't put it to sleep thinking it might be a sociopath and could kill again or grow up to be a killer. Obviously kids are valued more than pets and are seen more important than pets.