The pitbull breed can still be saved, we just have to consistently kill those who show aggressive behavior.
Edit: all right pitbulls are not all bad,some of them are even brave, I heard a story of how one died, a kid was trapped in a burning house, the pitbull seeing that, bravely broke into the house, so it could maul a child one more time.
I would be okay with them being persevered by zoos. They do not belong to the general public just like we don't tolerate private ownership of jaguars, hyenas, and other dangerous animals.