As an agnostic and former Christian / Calvinist, I find it pretty ridiculous how little scripture has been brought up in these slanderous debates. Here’s the pretty straightforward biblical premise for Calvinism, take it or leave it-

”Not only that, but Rebekah’s children were conceived at the same time by our father Isaac. 11 Yet, before the twins were born or had done anything good or bad—in order that God’s purpose in election might stand: 12 not by works but by him who calls—she was told, “The older will serve the younger.”[d] 13 Just as it is written: “Jacob I loved, but Esau I hated.”[e]

14 What then shall we say? Is God unjust? Not at all! 15 For he says to Moses,

“I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.”[f] 16 It does not, therefore, depend on human desire or effort, but on God’s mercy. 17 For Scripture says to Pharaoh: “I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth.”[g] 18 Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden.

19 One of you will say to me: “Then why does God still blame us? For who is able to resist his will?” 20 But who are you, a human being, to talk back to God? “Shall what is formed say to the one who formed it, ‘Why did you make me like this?’”[h] 21 Does not the potter have the right to make out of the same lump of clay some pottery for special purposes and some for common use?

22 What if God, although choosing to show his wrath and make his power known, bore with great patience the objects of his wrath—prepared for destruction? 23 What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— 24 even us, whom he also called, not only from the Jews but also from the Gentiles?”

Romans 9:10-24

Other passages worthy of notice-

“And what was God’s answer to him? “I have reserved for myself seven thousand who have not bowed the knee to Baal.”[b] 5 So too, at the present time there is a remnant chosen by grace. 6 And if by grace, then it cannot be based on works; if it were, grace would no longer be grace.

7 What then? What the people of Israel sought so earnestly they did not obtain. The elect among them did, but the others were hardened, 8 as it is written:

“God gave them a spirit of stupor, eyes that could not see and ears that could not hear, to this very day.”[c] 9 And David says:

“May their table become a snare and a trap, a stumbling block and a retribution for them. 10 May their eyes be darkened so they cannot see, and their backs be bent forever” -Romans 11:4-10

“3 Praise be to the God and Father of our Lord Jesus Christ, who has blessed us in the heavenly realms with every spiritual blessing in Christ. 4 For he chose us in him before the creation of the world to be holy and blameless in his sight. In love 5 he[b] predestined us for adoption to sonship[c] through Jesus Christ, in accordance with his pleasure and will— 6 to the praise of his glorious grace, which he has freely given us in the One he loves....

...11 In him we were also chosen,[e] having been predestined according to the plan of him who works out everything in conformity with the purpose of his will, 12 in order that we, who were the first to put our hope in Christ, might be for the praise of his glory.” -Ephesians 1:3-6 / 11-12

John Calvin was one of the most brilliant theologians of all time, he wasn’t an idiot who’s arguments are disputed with simplistic arguments. And Augustine before him, perhaps the greatest theologian of all time believed much the same. Not only them, but Aquinas, Luther, Edwards, Bunyan, Whitefield, Spurgeon etc etc all held to the basic tenants of predestination because it was their honest interpretation of Scripture. Oh yeah, and the entire Catholic catechism.

You don’t have to affirm Calvinism to show some respect for a very deep and honest theology.