The sovereign God “decides who will believe and undeservingly be saved and who will rebel and deservingly perish.”
—John Piper, “How God Makes Known the Riches of His Glory to the Vessels of Mercy,” sermon on Rom 9:19–23 (February 16, 2003). [Quote taken from http://andynaselli.com/framing-the-doctrine-of-election ]
Did you catch that Piper claims that God decides who will rebel? And then, those who rebel because God decided they would, somehow deserve to perish for that God-caused rebellion? And this does not make God the author of sin?
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.