Strange rumors were said by Pagans about Christians abandoning themselves to a lascivious and vicious way of life during their secret meetings, probable effect on a radically anti-nomian and therefore Gnostic view.15 While Jesus was having dinner at Levi’s house, many tax collectors and sinners were eating with him and his disciples, for there were many who followed him. 16 When the teachers of the law who were Pharisees saw him eating with the sinners and tax collectors, they asked his disciples: “Why does he eat with tax collectors and sinners?”
17 On hearing this, Jesus said to them, “It is not the healthy who need a doctor, but the sick. I have not come to call the righteous, but sinners.”
So here Jesus would be came just to save these "sinners". His gospel is addressed to their conversion. The alternative would be to abandon them to themselves (i.e allowing the existence of anti-nomian gnosticism). In this sense the Parable of Wineskins means that Jesus has to reedem these "new" Christians. The "old" Christians (the too much Torah-centered Christians) have not to hinder the process.