Uncontrolled dogs, those with or without proper owners, may pose great threat to the bodily well-being of the people, other animals and the surrounding environment. The trouble of uncontrolled dogs may range from excrement on public sidewalks to fatal dog bites. Negligence of dog owners and law enforcement officials contribute to the problem of vicious and unpredictable dog behaviour. The popularity of organized dog fighting may reinforce the mystique of owning a wild dog, as well may an individual's need to protect his home and family from harmful intruders. Abandoned dogs and those that are allowed to roam freely are real problems to wildlife as they compete with other predators and kill wild animals, disturb the ecosystem, transmit diseases to wildlife and also interbreed with closely related species.
In 1988, eight Americans were killed by pit bull terriers. At a District of Columbia Council hearing on the fortification of dog-bite laws during the same year, one member attempted to shield a dangerous breed by insisting all dogs are covered by the equal protection clause of the USA Constitution. The American pit bull terrier is the most ferocious dog known, according to the RSPCA. The Japanese Tosa, almost as large as a mule, is known as the "sumo wrestler" of the dog fighting world. Other dogs considered dangerous and unpredictable include rottweilers, bull terriers, Staffordshire terriers, wolf and Alsatian hybrids, Japanese Akita and Neapolitan Mastiffs.
In Belgium, ten thousand dogs are put down each year because of behavioural problems associated with inbreed aggression.
Banning so-called dangerous breed just strengthens the illegal market.