Uncleanness, sin and defilement were more powerful influences than cleanness, sanctity and purity.
In the old Law, sin was the superior power. When someone afflicted with some ritual uncleanness that symbolizes sin touched someone who was clean, the “flow” of power went in one direction only: The clean person was defiled but the unclean person was not sanctified.
But when Jesus touched the leper something astounding happened: The leper became clean and Jesus was not defiled. The flow of power was, for the first time, reversed.
Naturally then, the Pharisees simply do not know what to do with him and are motivated by their pride to misunderstand him.
It is the realization that we do indeed live under the New Covenant and that our primary mission as Catholics is to make the world holy, not to keep the world from defiling us. We have to learn that the Church ultimately has the upper hand against sin because we have the power of Christ. [emphasis added]