Sorry, the answer inevitably involves free will, beginning with Satan’s choice to deny God, and Adam’s choice to eat the forbidden fruit.
Do I take it that Sproul is a Calvinist who denies that God gives man the freedom to choose? If so, then, indeed, the explanation is difficult.
Two good places to start are Milton’s “Paradise Lost” and C. S. Lewis’s “The Problem of Pain.”
**Do I take it that Sproul is a Calvinist**
Yes
**who denies that God gives man the freedom to choose?**
No.
Man’s will is so corrupted he will always choose things against God’s will. But he does so freely.