There is no reason to ban the possesion of pit bulls. It will be the responcibility of the owner to train and take care of the animal and to make sure that it does not cause harm. There is an established correlation between the behaviour of an owner and how the owner treats the animal and the developed behaviour of the animal.
If, however, the animal causes harm, the owner must be reprimanded and the animal put down in order to prevent future problems.

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The Capitalist maxim: The fortunate must not be restrained in the exercise of tyranny over the unfortunate. Bertrand Russell
Heroism on command, senseless violence, and all the loathsome nonsense that goes by the name of patriotism -how passionately I hate them! ~Albert Einstein