1. Is Christ's death as a punishment for our sins ("penal substitutionary atonement") central to Christianity?
2. Is this teaching equal to "cosmic child abuse"?
YES. PENAL SUBSITUTIONARY ATONEMENT IS CENTRAL TO THE GOSPEL.
Yes. Penal substitutionary atonement is central to the Gospel and therefore to Christianity.
This is stated quite explicitly and emphatically in 1 Corinthians 15:1-4:
"Now, brothers and sisters, I want to remind you of the gospel I preached to you, which you received and on which you have taken your stand. 2 By this gospel you are saved, if you hold firmly to the word I preached to you. Otherwise, you have believed in vain. 3 For what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures, 4 that he was buried, that he was raised on the third day according to the Scriptures,...."
Note that Paul states that the Gospel is summed up as: Christ died for our sins, was buried and was raised again. And "Christ died for our sins" is clearly shorthand for PSA. And he does not merely say that this is the summary of the Gospel. He says that it is "of first importance" and that: "By this Gospel you are saved, IF you hold firmly" to it. "Otherwise you have believed in vain." This is all stated quite clearly and emphatically. And since is the Gospel, it is clear also that Paul declares the utmost condemnation on anyone who preaches another Gospel (Galatians 1:6-10).
So the fact that there are other implications of Christ's death that are taught in Scripture does not set aside the centrality of the penal substitionary atonement understanding of Christ's death. Only the penal substitutionary atonement of Christ's death brings cleansing of our sins; and if we are still in our sins, then our faith is useless. We are still condemned and separated from God for eternity. So yes the penal substitutionary atonement is absolutely central.
THIS IS TAUGHT THROUGHOUT THE SCRIPTURES
And the concept of penal substitutionary atonement is taught throughout the Scriptures:
Isaiah 53:4-6: Surely he took up our pain and bore our suffering, yet we considered him PUNISHED by God, stricken by him, and afflicted. But he was pierced for our transgressions, he was crushed for our iniquities; the PUNISHMENT that brought us peace was on him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to our own way; and the LORD has laid on him the iniquity of us all.
Isaiah 53:10-12: Yet it was the LORD’s will to crush him and cause him to suffer, and though the LORD makes his life an offering for sin, he will see his offspring and prolong his days, and the will of the LORD will prosper in his hand. After he has suffered, he will see the light of life and be satisfied[; by his knowledge my righteous servant will justify many, and he will bear their iniquities. Therefore I will give him a portion among the great, and he will divide the spoils with the strong, because he poured out his life unto death, and was numbered with the transgressors. For he bore the sin of many, and made intercession for the transgressors.
Matthew 26:28: This is my blood of the covenant, which is poured out for many for the forgiveness of sins.
Romans 3:25-26: God presented Christ as a sacrifice of atonement, through the shedding of his blood—to be received by faith. He did this to demonstrate his righteousness, because in his forbearance he had left the sins committed beforehand unpunished—he did it to demonstrate his righteousness at the present time, so as to be just and the one who justifies those who have faith in Jesus.
Romans 4:25: He was delivered over to death for our sins and was raised to life for our justification.
2 Corinthians 5:21: God made him who had no sin to be sin for us, so that in him we might become the righteousness of God.
Galatians 1:4: who gave himself for our sins to rescue us from the present evil age, according to the will of our God and Father,
Ephesians 1:7: In him we have redemption through his blood, the forgiveness of sins, in accordance with the riches of God’s grace
Hebrews 10:11-12: Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God,
1 Peter 2:24: “He himself bore our sins” in his body on the cross, so that we might die to sins and live for righteousness; “by his wounds you have been healed.”
1 Peter 3:18: For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit.
1 John 2:2: He is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world.
NO. CHRIST'S DEATH ON THE CROSS IS NOT "COSMIC CHILD ABUSE"
And No. The Scriptural teaching of Penal Substitutionary Atonement is not "cosmic child abuse." This is a very old slander brought against the Gospel by liberals/progressives who want to reduce the Gospel to moralistic deism (or in the last few decades panentheism....or any other worldview rather than Biblical theism). They bring this empty charge by divorcing the concept of penal substitutionary atonement from its context and cherry-picking only the details that serve their purpose.
First, Jesus is not a mere human child--powerless under the sway of a manipulative human father. He is God incarnate. He is co-eternal and equal and one with the Father, in the incomprehensible mystery of the Triune Godhead. And everything they do is done first out of love for each other and then out of love for their creation.
Second, Jesus is explicit when he says: "No one takes it from me, but I lay it down of my own accord" (John 10:18). And even as he is being arrested, he is clear that he has the power to back out at any moment: "Do you think I cannot call on my Father, and he will at once put at my disposal more than twelve legions of angels?" (Matthew 26:53).
So this is clearly not child abuse of any kind or anything like it. This is more like a father sending his child off to war to defeat an evil foe and bring about justice--with tears of great sorrow in his eyes but knowing that it must be done. And the son goes off to war with the same conviction as the father and with a mixture of dread overcome by great courage and desire for justice. It is more like this, but much more so.
GOD IS A JUST JUDGE
Consider the clear implications of Romans 3:25-26:
"God presented Christ as a sacrifice of atonement, through the shedding of his blood—to be received by faith. He did this to demonstrate his righteousness, because in his forbearance he had left the sins committed beforehand unpunished—he did it to demonstrate his righteousness at the present time, so as to be just and the one who justifies those who have faith in Jesus."
God is a just Judge because he requires punishment for lawbreakers. What kind of judge simply forgives everyone who comes before them? Such a judge would make a mockery of justice by ignoring all the harm done by every criminal.
But God is both just and justifier because he provides that punishment for all through the voluntary death of his eternal Son who took our punishment upon himself, once for all time.
