Given that the typical pit bull owner can't tell his head from his posterior on any given day, we should just lump them all together.
This thing where someone has to have a "purebred" dog should also be retired. Mutts are generally better, anyways. Purebred shoppers are the ones subsidizing breeders, many/most of whom are unethical and sloppy.
Finally, I'm all on board with keeping pit bulls legal, provided we administer a very simple test for prospective owners. A two or three question survey:
1. Have you ever done time?
2. Have you used illegal drugs after you turned 25?
And since we probably won't get truthful, verifiable answers to #2, we would need to administer a drug test.
Those two questions alone would eliminate 100% of the miscreants. Not a one of them can pass that simple test. Those two things are true of basically every lowlife. They've done time and they'll do time again, and they've abused dope past that age where a normal person can no longer blame it on an undeveloped brain and have entered the pathetic, "I'm self-medicating because I can't deal with my issues and weaknesses" realm. Those folks should not own animals of any sort that can easily kill other people. We already know that their judgment is non-existent and they're bereft of morals.