Don't forget, Jesus was also setting the stage for what He knew was coming and what He would be going through. Even though Jesus Himself followed the law because His time had not come yet, He still chose certain instances considered unlawful, for teaching purposes. I think the lesson regarding the adulterous woman was to show the law givers their own law breaking and self righteousness.
This is good. I agree. But when they disobey anyway, how many times do you talk to them?
Until they hear?
I have a lot of trouble relating to the idea that when Jesus comes back his two-edged sword is anything other than his tongue and his words. God is unchanging, we are told. Covenants typically have gotten lest stringent and violent as man has become more intelligent and God shows himself more, but his 'demeanor' if you can call it that, is typified at its most revealing in how Jesus behaves. When Jesus came, he came with forgiveness, compassion and wisdom. It makes no sense that he would change his character into some barbaric slayer upon his return, after preaching forgiveness for so long.
Proverbs is Hebrew, OT, and thus some of it is violent. Yet we see a many great lawful teachings and violent instructions overturned or negated in the NT by Jesus. It is the matter of righteousness being higher than lawfulness.
Similarly to this, I think that the parent who resorts to hitting the child does so because they cannot think of any other means to communicate with the child; a lack of the wisdom to reach the child; a wisdom that Jesus does not lack.
While no human parent is perfect, it is also true that no child asks to be brought into the world. In my opinion, the giving of life and ultimately the fact that people have to come to terms with eventual death is even in itself enough means to treat everyone, particularly the defenseless children, without violence or violation.
Jesus tells us that he brings a 'sword', then says that children shall rise up against parents, young against old. I believe this isn't a physical rising up, but a moral one.
Our generation, particularly those my age, generally believe in parenting and behaving in very different ways than generations gone by. It is a stereotype, albeit a true one, that families 'back then' tended to be more physical and violent. I, however, do not see that as a wise thing, but a step backwards.