The punishment of the ben sorer u'moreh seems far more severe than the crime. For stealing meat and wine from his parents, no more than a little gluttony, he is liable for the death penalty (after first being warned by Beis Din not to repeat the offense and then doing so). Chazal explain that he is "ne'herag al shem sofo", he is killed because the Torah anticipates that this behavior portends a life of crime and evil. Better the ben sorer u'moreh should die while mostly innocent than be allowed to develop into an antisocial, wicked, harmful adult.
Yet, if the parents of the ben sorer u'moreh decide at the last minute to grant mechila to their child, he is released without punishment (Sanhedrin 88). This seems odd. If we anticipate this this individual with develop into a criminal, why spare his punishment now just because his parents got cold feet and want to let him off the hook? Why should society be subject to the danger of the ben sorer u'moreh because of his parents forgiveness?
The Shem m'Shmuel answers that so long as his parents are willing to forgive past transgressions and make an attempt to rehabilitate him, the ben sorer u'moreh cannot be written off. Only once even the ben sorer u'moreh's parents give up, only once that bond between generations is broken, is there truly no hope left.
As touched on in the comments to the last post, the ben sorer u'moreh teaches us more than about the tragedy of the rebellion of youth -- it also teaches us about our responsibility as parents to respond to that rebelliousness. Mechila here does not mean tolerance of crime; it means willingness to forgive in the hope of improvement, change, and growth. It is having parents who are willing to accept the challenge of dealing with a ben sorer u'moreh and guiding him to positive growth which allows his life to be spared.
I recently saw in the sefer on the hanahagos of the Steipler (sorry, forgot the exact title) that he made a point of learning daily with his son R' Chaim. He also made a point of learning with his daughters. When R' Chaim married, the Steipler continued to have a weekly seder with his son and together they leaned the entire Yerushalmi, Midrashei aggadah and halacha, and other seforim. I am willing to guess that the Steipler was a pretty busy Rabbi and R' Chaim Kanievsky was probably a pretty good student who did not need his father's tutoring. But its that personal bond, that parent-child relationship, which would have been lacking had they not had that seder together. No matter how good a child's yeshiva is, there is no substitute for the chinuch of the home and the personal responsibility taken by parents to ensure a child develops in Torah properly.