See my thread:
Quoting Calvin.
3. It eliminates free will and human responsibility
We hold that God is the disposer and ruler of all things, –that from the remotest eternity, according to his own wisdom, He decreed what he was to do, and now by his power executes what he decreed. Hence we maintain, that by His providence, not heaven and earth and inanimate creatures only, but also the counsels and wills of men are so governed as to move exactly in the course which he has destined. (John Calvin, Institutes of Christian Religion, Book 1, Chapter 16, Paragraph 8)
Creatures are so governed by the secret counsel of God, that nothing happens but what he has knowingly and willingly decreed. (John Calvin, Institutes of Christian Religion, Book 1, Chapter 16, Paragraph 3)
God causes everything and of necessity, that is, in accordance with his providence. (John Calvin, The Bondage and Liberation of the Will, 1996, pg. 253)
Everything that happens, happens of necessity, as God has ordained. (John Calvin, The Bondage and Liberation of the Will, 1996, pg. 258)
5. It makes God a moral monster
...how foolish and frail is the support of divine justice afforded by the suggestion that evils come to be, not by His will but by His permission... It is a quite frivolous refuge to say that God otiosely permits them, when Scripture shows Him not only willing, but the author of them... (John Calvin, The Eternal Predestination of God, 10:11)
The devil, and the whole train of the ungodly, are in all directions, held in by the hand of God as with a bridle, so that they can neither conceive any mischief, nor plan what they have conceived, nor how muchsoever they may have planned, move a single finger to perpetrate, unless in so far as he permits, nay unless in so far as he commands, that they are not only bound by his fetters but are even forced to do him service (John Calvin, Institutes of Christian Religion, Book 1, Chapter 17, Paragraph 11)
thieves and murderers, and other evildoers, are instruments of divine providence, being employed by the Lord himself to execute judgments which he has resolved to inflict. (John Calvin, Institutes of Christian Religion, Book 1, Chapter 17, Paragraph 5)
…it is utterly inconsistent to transfer the preparation for destruction to anything but God’s secret plan… God’s secret plan is the cause of hardening. (John Calvin, Institutes of Christian Religion, Book 3, Chapter 23, Paragraph 1)
…individuals are born, who are doomed from the womb to certain death, and are to glorify him by their destruction. (John Calvin, Institutes of Christian Religion, Book 3, Chapter 23, Paragraph 6)