why do so many catholics believe in Penal substitution?

I am becoming ever more convinced that there is a wide spread lack of understanding amongst Catholics of the nature of the Atonement. St. Anselm, pray for us. I have heard it in homilies, I have read it in books by popular Catholic theologians and apologists, I have heard on Catholic talk radio, I have discovered it in working to prepare 8th graders for confirmation: the Protestant theory of Christ's atonement known as penal substitution. Penal substitution, simply put, is the theory that Christ was punished on the Cross with the punishment with which we deserved to be punished. Here is a great example in a work by a very popular Catholic philosopher and a Jesuit priest:

"It seems impossible for God to solve the dilemma of justice versus mercy, but we know from the Gospel account how he does it. The problem is that he cannot, it seems, do both; he must either exact the just penalty for sin - death - or not. Mercy seems a relaxation of justice, and justice a refusal of mercy. Either you punish or you don't. The laws of logic seem to prevent God from being both just and merciful at the same time... God solves this dilemma on Calvary. Full justice is done: sin is punished with the very punishment of hell itself - being forsaken of God (Mt 27:46). But mercy and forgiveness are also enacted. The trick is to give us the mercy and him the justice" (Handbook of Christian Apologetics by Peter Kreeft and Ronald K. Tacelli, p. 127).

I have seen and heard Christ's atonement described in such ways by Catholics time and time again. There are a number of gaping flaws in this Protestant theory: first, what is just about condemning an innocent man to die in another's place? And what happens to the concept of forgiveness if God does, in fact, exact the full punishment for sin, just from another party? According to this theory, God's righteous anger against us is not withheld but merely redirected. Furthermore, if Christ is supposed to suffer the punishment that we all ought to have suffered on account of sin, simply dying certainly wouldn't cut it, the punishment of sin is eternal separation from God - He would have to accept this. The authors above try to deal with this by pointing to Matthew 27:46 "My God, my God, why have you forsaken me?" as if this points to a real separation between Father and Son. Anyone, however, who is familiar with Trinitarian theology knows this to be absurd. The Persons of the Godhead are certainly inseparable. Even if Matthew 27:46 did indicate a separation of the Son from the Father, the punishment of sin, which He is supposedly accepting, is eternal separation from God, not a three day separation from God. Again, if Christ has actually been punished for all sins committed throughout all time by all men, what is to stop us from sinning freely? God would be unjust to punish both Christ and us for the same sin, and having alreadly punished Christ, He could not punish us. This leads swiftly into one of two places, universalism - the belief that all will be saved, or Calvinist double predestination - wherein Christ only died to save some men. This solves the problem by positing that Christ accepted the punishment only for the elect and therefore God can still punish the damned (this does still leave the elect free to sin without fear).

Why, then, do explanations like Kreeft's and Tacelli's above seem to be so widespread in popular Catholic thinking? And what is the big deal? Here is a hint: there is one more major problem with the Protestant theory of penal substitution. It leaves no room for a perpetual sacrificial propitiation for sins, i.e. the Holy Sacrifice of the Mass. Think about it. If Christ, in dying on the Cross, accepted the punishment then and there of all men, what need is there for a continual sacrifice, the purpose of which is to appease God's anger and assuage His wrath? None. The only sensible purpose of the Mass then would be to provide us an opportunity to receive Him sacramentally in Holy Communion (and I know many Catholics who see this as the primary, indeed the only, purpose of the Holy Mass). This, I think, goes a long way to explaining the inverted emphasis on the meal/communion aspect of the Mass over against the sacrificial aspect of the Mass. When one's understanding of the atonement is so far Protestantized as to think in terms of penal substitution, it is hard to see why the Mass should really be anything more than a Communion service.

If I could be so bold as to add another step into Fr. Z's famous plan to save the world: Understand the Atonement; Save the Liturgy; Save the World! St. Anselm, ora pro nobis!

P.S. I wrote this assuming our esteemed readership to be sufficiently familiar with Catholic theology as to know what the Catholic theory of the Atonemen, admirably explained by St. Anselm, really is. To refresh your memory, see St. Anselm's Cur Deus Homo? and the Catholic Encyclopedia.
Posted by Anselm