Well, there's the law of Moses, and then there's the law of Moses. Inasmuch as he walks and talks like a Pharisee, Jesus was another participant in the constant renegotiation and reappraisal of the Mosaic law. Of course, you're still welcome to pass on it, but Jesus did not have some literalist take on the law, and not just because such a thing is impossible. Just like every Pharisiac interpreter, he could go stricter: no divorce! He could also go more lenient: don't cast stones, though that story is a later interpolation, i.e., it's definitely ahistorical.
Long story short--yeah, slaves were ok, but I don't think scholars have actually concluded that practical, on-the-ground jurisprudence resulted in people constantly stoning impudent children and the like.