score:9
The Westminster Confession of Faith (the doctrinal standard for many Presbyterians), Chapter III, makes it clear that at least one well recognized portion of Calvinists firmly rejects the claim that God is the author of evil (emphasis added):
I. God from all eternity did by the most wise and holy counsel of his own will, freely and unchangeably ordain whatsoever comes to pass; yet so as thereby neither is God the author of sin; nor is violence offered to the will of the creatures, nor is the liberty or contingency of second causes taken away, but rather established."
Point VII might also be worth mentioning (emphasis added):
VIII. The doctrine of this high mystery of predestination is to be handled with special prudence and care, that men attending to the will of God revealed in his Word, and yielding obedience thereunto, may, from the certainty of their effectual vocation, be assured of their eternal election. So shall this doctrine afford matter of praise, reverence, and admiration of God; and of humility, diligence, and abundant consolation to all that sincerely obey the gospel.
This clearly shows that these Calvinists recognized such as a "high mystery" and vulnerable to careless interpretation and application.
On the "please elaborate" front, I think Calvinists are trying to embrace God's omnipotence, omniscience, and Goodness (and pancracy--all-ruling, "Almighty" in Revelation) while still recognizing the presence of evil in the world--all of which are strongly witnessed in Scripture. Accepting God's absolute sovereignty and goodness (so could not be the author of evil) and the presence of evil results in a logical problem that is resolved by assuming that the understanding of the terms is inadequate (i.e., mystery). This, of course, does not mean that one should reject one's partial understanding of the terms even when one does not yet know how they are reconciled.
Upvote:-3
Again, Calvinism isn't monolithic in its views across the board.
Quote from Pen and Parchment article:
As I assumed, upon further investigation, Keathley’s assessment was correct: Sproul Jr. has simply taken Calvinism way too far. His father R.C. Sproul Sr., also a Calvinist, has been much more tentative and modest about the question of sin’s starting point; he basically concludes that this is a mysterious matter, stopping well short of attributing the origin of evil to God:
Herein lies the problem. Before a person can commit an act of sin he must first have a desire to perform that act. The Bible tells us that evil actions flow from evil desires. But the presence of an evil desire is already sin. We sin because we are sinners. We were born with a sin nature. We are fallen creatures. But Adam and Eve were not created fallen. They had no sin nature. They were good creatures with a free will. Yet they chose to sin. Why? I don’t know. Nor have I found anyone yet who does know” (Chosen by God [1986], p. 30).
Upvote:2
It depends on the Calvinist:
[Christ] works all things according to the counsel of his will. [This] indicates that God not merely carries all of the universe’s objects and events to their appointed ends but that he actually brings about all things in accordance with his will. In other words, it isn’t just that God manages to turn the evil aspects of our world to good for those who love him; it is rather that he himself brings about these evil aspects for his glory and his people’s good. This includes—as incredible and as unacceptable as it may currently seem—God’s having even brought about the Nazis’ brutality at Birkenau and Auschwitz as well as the terrible killings of Dennis Rader and even the sexual abuse of a young child.
Reference: Mark Talbot, "“All the Good That Is Ours in Christ”: Seeing God’s Gracious Hand in the Hurts Others Do to Us", in John Piper and Justin Taylor (ed.), Suffering and the Sovereignty of God. Wheaton, Ill: Crossway Books, 2006, pp. 41-42