The Holy Father explains - if you read far enough - that evil is neither equal and opposite to the good of being, nor simply a part of a mindless, arbitrary evolutionary model of the universe. Rather,
This, if you will remember, is why Our Lord not only proclaimed the good news of God's Kingdom, but also healed and cured in the days of His flesh. The fallen world is not as God intended creation. If we are to be one-with His mission, pledging fealty and partaking in a quest of Marian chivalry, we must stay close to Him; do as He did and does.
"Evil comes from a subordinate source. With his light, God is stronger and, because of this, evil can be overcome. Therefore, the creature, man, is curable; […] man is not only curable, he is in fact cured. God has introduced healing. He entered in person into history. To the permanent source of evil he has opposed a source of pure good. Christ crucified and risen, the new Adam."
Do not fight the fire of evil with its own fire. Fight it with the waters of our Baptism; put on the armor of God; and sing merrily with our good companions who dine with us on Panis angelicus. Deo gratias.