In a book edited by John Piper, Calvinist philosopher Mark R. Talbot writes:
God . . . 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 (see Ex. 9:13-16; John 9:3) and his people’s good (see Heb. 12:3-11; James 1:2-4). 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 . . .
— Mark R. 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 (eds.), Suffering and the Sovereignty of God (Wheaton: Crossway, 2006), 31-77 (quote from p. 42).
That is massively unbiblical and horrific, and would seem to be John Piper’s view as well, who shares Talbot’s theology that God unconditionally decreed all things (indeed, you can hear John Piper affirming that God does decree all abuse against children and trying to give a rationale for it at around the 26 minute mark of this audio). It is baffling and astonishing that Calvinists hold that God first conceived in his own divine heart every evil human act, including every act of sexual abuse of young children, thought them all up without any influence outside of himself, and unconditionally and irresistibly decreed them without any influence outside of himself, resulting in the perpetrators doing them all without any chance, power, or ability to do anything else. (That is simply what God unconditionally decreeing all things entails.)
We know that many Calvinists believe such unbiblical and seemingly heinous things. But thankfully, it remains shocking to hear them state it so plainly. Otherwise, perhaps we should Recover a Sense of Incredulity over Calvinism as Jim Leonard has suggested here.