There is a proverb that reads as follows:
The poor and the oppressor have this in common:
the LORD gives light to the eyes of both (Prov 29.13).
I understand from this proverb that God is inextricably connected to all the persons whom we meet and whom we affect in our day-to-day interactions. Importantly, God gives each and every one of us light, life, health, movement of body in every passing moment. It is God's desire that a person lives and comes to know him.
For this reason, to harm another person is to act against God. While God desires that person's life, you desire her death and suffering. While God desires that person to come to know him, you make this impossible because, bearing the name of a Christian, you act like a son of the devil. While God wants this person to do well in the world, you are opposing the will of heaven by seeking her downfall and misery.
Christ told us that this principle will be used in the final judgment: whatsoever you did unto others, you did unto Christ who is concerned for those others (Mt 25.31-46). True wisdom sees God behind every person, and lives accordingly.