Her comment reveals both a discomfort that many contemporary Christians have with God's wrath and also an overly simplistic dismissal of penal substitution. We who believe the Son bore the Father's wrath don't narrowly think that assuaging this wrath is what the cross is "primarily" about. What happened on the cross is a bit more complicated.
All orthodox theories of the atonement fall into three or four main categories (depending on how sharply you separate moral influence from the example theory), and the four arms of the cross supplies a handy model for remembering them:
The cross is aimed:
1. Downward, toward Satan: The early church emphasized this Christus Victor aspect of the cross, which said Jesus died to defeat Satan, who held the power of sin and death (Colossians 2:15; Hebrews 2:14-15; 1 John 3:8).
2. Upward, toward God: Popularized by Anselm and Calvin, penal substitution explained that Jesus satisfied the Father's wrath by bearing our penalty in our place (Romans 3:25-26; Galatians 3:13; 2 Corinthians 5:21; 1 John 2:2; 4:10).
3. Sideways, toward us: Abelard, a contemporary of Anselm, said the cross provides a moral influence by showing us how much God loves us (1 John 3:16; 4:7-12; Romans 5:8). Socinians and liberal Christians said the cross is merely a human Jesus providing a moral example that inspires us to love and trust God. Though Socinians and liberals wrongly deny Jesus' deity, they rightly note that on the cross Jesus "suffered for you, leaving you an example, that you might follow in his steps" (1 Peter 2:21). The moral influence and example theory differ on whether the action on the cross is moving from God to us or from us to God, but they agree that its effect is on the human person rather than on God or the devil.
The fact that all of these theories have biblical support leads some to suggest they must be equally important. They say that none is more primary than another, but each supplies an equally significant reason for the cross.
But why would we think this way? If I asked why you wanted to get married, you might come up with lots of reasons. You might talk about love, your desire for companionship, sex, children, and to save money on taxes by filing jointly. Yet no one would suggest these are equally significant reasons for marriage. Some represent the goal of marriage, others the means to that goal, and still others the benefit of having reached the goal. I'll let you figure out which is which, assuming that any guy romantic enough to propose marriage has enough sense to give the right answer if asked by his fiancé (hint: it's not about the money).
Every action has a goal, a means to reach that goal, and a payoff for reaching it. This is true about getting married, going to work, even reading this article. It's also true about why Jesus died.
The Goal: Christus Victor
Ask informed evangelicals why Jesus died and they will likely respond with a paraphrase of 2 Corinthians 5:21. Jesus who knew no sin became sin for us, "so that in him we might become the righteousness of God." This is an excellent statement of penal substitution, but what is its larger purpose? What does becoming God's righteousness lead to?
The answer is supplied by Christus Victor. God doesn't satisfy his wrath for its own sake—he could have chosen to leave his wrath unquenched and save no one—but for the sake of delivering us from hell. Hebrews 2:14-15 explains that Jesus died to "destroy the one who has the power of death, that is, the devil, and deliver all those who through fear of death were subject to lifelong slavery."
The primary reason Jesus died, the main goal of the cross and resurrection, was to defeat sin, death, and Satan. In our rightful zeal to defend the truth of penal substitution, we must remember to always place it into this larger picture. Penal substitution is the means to the end, not the end itself.
The Means to Reach the Goal: Penal Substitution
But what an essential means it is! It's increasingly popular today for supporters of Christus Victor to say that Jesus can defeat sin, death, and Satan without bearing the Father's wrath. Indeed, they say the Father is too kind to have wrath that must be appeased. But these theologians quickly run into two large problems.
1. The Old Testament. The Jews regularly sacrificed animals as a substitute for sin. Spotless lambs, which foreshadowed the innocent Lamb of God, bore God's wrath in the worshipers' place. In The Nature of the Atonement: Four Views, Greg Boyd and Joel Green say this popular view is wrong, for the sacrificial animals were not bearing God's penalty or wrath.
They both cite an essay by John Goldingay, who writes:
Sacrifice does not involve penal substitution in the sense that one entity bears another's punishment. By laying hands on the offering, the offerers identify with it and pass on to it not their guilt but their stain. The offering is then not vicariously punished but vicariously cleansed.
Goldingay doesn't cite any other source, so I can only evaluate his claims on their own merits. I notice that he doesn't supply an argument for his view that the animals were euphemistically "cleansed" rather than "punished," and changing the words doesn't change the reality. Where I live hunters "harvest" deer rather than "kill" them, but the result is pretty much the same for the animal. Henri Blocher rightly wonders, "When J. Goldingay claims that offerers 'pass on to [the victim] not their guilt but their stain,' we ask: what is the spiritual stain of sin if not their guilt before God?"
2. Those who deny penal substitution are unable to explain how the cross defeats sin, death, and Satan. Greg Boyd admits this much about his Christus Victor view:
Obviously, this account leaves unanswered a number of questions we might like answered. E.g., precisely how did Calvary and the resurrection defeat the powers? In my estimation, the ancient Christus Victor models of the atonement . . . became incredulous precisely because they too vigorously pressed for details. . . . But at the end of the day we must humbly acknowledge that our understanding is severely limited.
If removing penal substitution means you can no longer say how the cross defeats sin, death, and Satan, perhaps you should take it as a sign that you took away something essential. In this way penal substitution is primary, because it explains precisely how Jesus defeated his enemies on the cross.
Benefits for Having Reached the Goal: Moral Influence and Moral Example
These are not the most important benefits of the cross, as it's hard to top defeating sin, death, and Satan by becoming the righteousness of God. But these are necessary consequences. We who have received such love from God must follow Jesus' example and love others on his behalf.
As with Christus Victor, these theories flounder without penal substitution. Many who emphasize the moral influence and example theories accuse penal substitution of advocating divine child abuse. Why would the Father demand the death of his innocent Son in order to forgive us? Why can't he be more like us and simply forgive without strings attached?
A couple of quick points (see chapter 6 of Don't Stop Believing for more detail):
First, there is no free lunch, either in economics or salvation. Someone always pays. The only reason we are free to forgive without sacrifice is because Jesus already paid it.
Second, the cross isn't an act of love without penal substitution, because love is only love if it does something. If the cross isn't necessary for God to forgive us, then what would be the point? If the cross is merely God expressing his solidarity with sinners, then why didn't he simply use his outdoor voice and say, "Attention, people of Earth! I love you and I'm on your side!" The Father was silent when his Son begged for any other way, which proves that God believes the cross was necessary to defeat sin, death, and Satan. And the only candidate that purports to explain why is penal substitution.
Third, those who deny penal substitution are the ones with a genuine case of divine child abuse, for their Father sacrifices his Son for no reason, or at least a reason that they know of.
I can illustrate the relationship between the theories with a cake. Christus Victor is the cake itself—the thing that Jesus was doing on the cross. Penal substitution supplies the ingredients, the flour and sugar. And moral influence and example are the frosting, the lingering sweetness of our great salvation. The cross assures us that we are loved, and it motivates us to love others as God has loved us.
Christus Victor explains why Jesus died, penal substitution explains how his death worked, and the double-sided moral influence and example theories explain what we should do in response.