How can God 'repent of the evil' He planned in Exodus 32:14 if He is all good?

First, what is the evil? In Hebrew the word for evil, ra, depends on context; it does not have to mean something immoral. When God is the one acting, the evil is a negative thing coming into your life, a punishment or destruction, an adjudication for the evil you have done, almost a tit for tat: God's evil is not immoral, because it is just. So the Old Testament uses ra for an action of God that is not unjust. As for the repentance, God shows his change of mind to Moses, because it was to Moses that he said he would destroy these people for the golden calf. Moses pleaded and God relented, though he still killed some of them, so the appeasement was not perfect. Moses gave two weak arguments: that the Egyptians would think God bad, which puts God on the spot over what men think, and that God promised the land to Abraham's seed forever, which God never said, since forever applies only to Abraham and his seed and refers to the future new heaven and new earth. Yet because God loves Moses and speaks to him face to face, he relents, as a loving father does with a little brother who does not know what he is asking for.