Cosmic child abuse?

A common objection that I hear from non-believers when they first hear the gospel is that it is "cosmic child abuse." A good, loving, and just God would never sacrifice Christ, an innocent third party, instead of the people who deserve judgement. In addition, many people refuse to accept Christianity on the grounds that they themselves would never want to put their sins on Christ, or subject Him to that kind of punishment. They would rather bear the guilt on their own. Here is a quote from "The Cross of Christ" that explains that the cross is anything but cosmic child abuse.

We began by showing that God must "satisfy himself," responding to the realities of human rebellion in a way that is perfectly consonant with his character. This internal necessity is our fixed starting point. In consequence, it would be impossible for us sinners to remain eternally the sole objects of his holy love, since he cannot both punish and pardon us at the same time. Hence the second necessity, namely substitution. The only way for God's holy love to be satisfied is for his holiness to be directed in judgment upon his appointed substitute, in order that his love may be directed toward us in forgiveness. The substitute bears the penalty, that we sinners may receive the pardon. Who, then, is the substitute? Certainly not Christ, if he is seen as a third party. Any notion of penal substitution in which three independent actors play a role -- the guilty party, the punitive judge and the innocent victim-- is to be repudiated with the utmost vehemence. It would not only be unjust in itself but would also reflect a defective Christology. For Christ is not an independent third person, but the eternal Son of the Father, who is one with the Father in his essential being.

What we see, then, in the drama of the cross is not three actors but two, ourselves on the one hand and God on the other. Not God as he is in himself (the Father), but God nevertheless, God-made-man-in-Christ (the Son). Hence the importance of those New Testament passages that speak of the death of Christ as the death of God's Son: for example, "God so loved the world that he gave his one and only Son" (John 3:16), "he... did not spare his own Son" (Romans 8:32), and "we were reconciled to God through the death of his Son" (Romans 5:10). For in giving his Son he was giving himself. This being so, it is the Judge himself who in holy love assumed the role of the innocent victim, for in and through the person of his Son he himself bore the penalty that he himself inflicted. As Dale put it, "The mysterious unity of the Father and the Son rendered it possible for God at once to endure and to inflict penal suffering." There is neither harsh injustice nor unprincipled love nor Christological heresy in that; there is only unfathomable mercy. For in order to save us in such a way as to satisfy himself, God through Christ substituted himself for us. Divine love triumphed over divine wrath by divine self-sacrifice. The cross was an act simultaneously of punishment and amnesty, severity and grace, justice and mercy.

Seen thus, the objections to a substitutionary atonement evaporate. There is nothing even remotely immoral here, since the substitute for the law-breakers is none other than the divine Lawmaker himself. There is no mechanical transaction either, since the self-sacrifice of love is the most personal of all actions. And what is achieved through the cross is no merely external change of legal status, since those who see God's love there and are united to Christ bye his Spirit become radically transformed in outlook and character.