I already suggested this in another comment, but you can easily apply a thought experiment here. Magically replace all white people with black people with the same upbringing: does crime go up, down, or basically stay the same? Magically replace all pitbulls with chihuahuas with the same upbringing: do maulings go up, down, or basically stay the same?

Couldn't tell the cops if the mugger was white or black? Pretty understandable. Couldn't tell the cops if the dog that bit you was a chihuahua or a pitbull? Really?

Any “big dog with a blocky head” should be banned from breeding or sale, and nobody who agrees with that statement cares about DNA. It is a matter of public safety and it doesn't matter that humans are the real problem, because humans are notoriously hard to control. The pitbulls and similar breeds we have today deserve all the love and comfort we can give them now, but they shouldn't be bred into the future because there is no legitimate reason to own one except for its potential for violence and flatulence-scapegoating.