Can Classical Protestantism Affirm the Lord's Prayer?

Called to Communion had a great discussion on this topic in regards to Calvinism, but I wanted to look at the same thing in regards to traditional Lutheranism. Pastor Hemmer of Hope Lutheran Church contrasts the Lutheran position with Catholicism quite neatly:

Can you be forgiven of sins you have not yet committed? 

The answer to this question exposes a huge difference between Lutherans and Roman Catholics in their understanding of forgiveness. Case in point: Baptism. For a Roman Catholic, in Baptism, God only forgives past sins. For a Lutheran, when God baptizes you, He places you into His forgiveness. That forgiveness covers past sins, current sins, and future sins. As Luther explained it, we live in our Baptism every day. 

So, to the person who is worried that Jesus might return before he has the chance to confess sins and receive forgiveness for those sins, the answer is, “Yes, as long as you remain in the forgiveness delivered to you at Baptism, you are already forgiven of those future sins.” There’s no partial forgiveness. Either all of your sins are answered for by Jesus or none of them is.

Contrast this with the Lord's Prayer (Mt. 6:9-13), in which we pray, "Give us this day our Supersubstantial [or Daily] Bread, and forgive us our debts, as we also forgive our debtors" (Mt. 6:11-12).  There are two things to note about this prayer:

1. We're asking God for forgiveness whenever we pray this, not thanking Him for forgiveness He's already delivered;
2. The forgiveness is conditional: conditioned upon us also forgiving.

It was this second point which Christ knew would be controversial. Out of the entire Lord's prayer, Jesus saw fit to comment only on this part. So immediately after teaching the Disciples the prayer, He said (Mt. 6:14-15):

For if you forgive other people when they sin against you, your heavenly Father will also forgive you. But if you do not forgive others their sins, your Father will not forgive your sins.

So whether your sins are or are not forgive is premised off of whether or not you forgive others their sins. That's a tough message, but it's one that Christ could scarcely make clearer. Strangely, Martin Luther, in his Larger Catechism explicitly denies that this condition exist, even while quoting to the passage, and making clear that the forgiveness is available only to those who forgive:

If, therefore, you do not forgive, then do not think that God forgives you; but if you forgive, you have this consolation and assurance, that you are forgiven in heaven, not on account of your forgiving, for God forgives freely and without condition, out of pure grace, because He has so promised, as the Gospel teaches, but in order that He may set this up for our confirmation and assurance for a sign alongside of the promise which accords with this prayer, Luke 6:37: Forgive, and ye shall be forgiven. Therefore Christ also repeats it soon after the Lord's Prayer, and says, Matt. 6:14: For if ye forgive men their trespasses, your heavenly Father will also forgive you, etc.

The problem appears to be that Luther couldn't understand how God's forgiveness could be pure grace, a free gift, and yet still conditional. But the problem is easily solved: a gift can still be conditional without us earning it.  For example, if I say, "if you swing by my house later today, I'll give you the keys to a brand new car," you don't somehow merit the gift by coming over. But if you refuse to show up to the house, you reject and deny the free gift. So it is with the forgiveness of God: we're given this free gift conditioned (again, rather explicitly) upon our forgiveness of others.

That's not just an idle hypothetical. In Matthew 18:23-35, a King freely forgives a servant a large debt (Mt. 18:27).  The servant then refuses to forgive a fellow servant a small debt (Mt. 18:28-30). So the King retracts the forgiveness, and turns him over to be tortured until the debt is paid (Mt. 18:34). Christ concludes: “This is how my heavenly Father will treat each of you unless you forgive your brother from your heart” (Mt. 18:35).  That's really straightforward: even if we've already been forgiven by Christ, that forgiveness can be taken away if we refuse to forgive others.  The servant wouldn't have merited being forgiven 10,000 talents (the equivalent of millions of dollars) by forgiving his brother servant the hundred denarii (the equivalent of a few dollars) he was owed.  The forgiveness is both a grace and conditional. So Luther's extreme opposition to any meritorious action on the part of the individual (for fear that this would lead to us "working our way to Heaven") meant that he couldn't understand Mt. 6:14-15, or Mt. 18:23-35, or any of the other passages which speak about the condition of forgiveness As a result, his explanation of the passage is something of a mess.

Calvin's is no better, in which he simultaneously declares Mt. 6:12 to be a condition, stating that "This condition is added, that no one may presume to approach God and ask forgiveness, who is not pure and free from all resentment," and yet proceeds to argue that "the forgiveness, which we ask that God would give us, does not depend on the forgiveness which we grant to others."  Now, it either is or isn't a condition. Calvin's attempt to have it both ways results in this embarrassing conclusion: "Christ did not intend to point out the cause, but only to remind us of the feelings which we ought to cherish towards brethren, when we desire to be reconciled to God." So rather than a condition of God's forgiveness, like Christ explicitly says, Calvin's position is that Christ decided to throw into the Lord's Prayer a short reminder about our feelings. But every Christian knows that there are times when we don't feel like forgiving our neighbor.  So Calvin's interpretation renders the condition of Matthew 6:12 and 6:14-15 to be simply advisory.  We ought to forgive others, but it's not necessary to be forgiven. Contrast that with Jesus Christ: "if you do not forgive others their sins, your Father will not forgive your sins" (Mt. 6:15). It's a condition of forgiveness, not a feel-good admonition about feelings, period.

Conclusion

A Lutheran or a Calvinist could affirm something like:

1. We forgive others because Christ has forgiven us first; and
2. Only through the grace of God are we able to truly forgive.

So a prayer like, "Thank you, Lord, for having forgiven me of my sins; out of gratitude, I shall try to forgive others" would be completely compatible with their faiths.  But that's not what the Lord's Prayer says. It says,  "forgive us our debts, as we also forgive our debtors",  and Christ tells us that means that "if you forgive other people when they sin against you, your heavenly Father will also forgive you. But if you do not forgive others their sins, your Father will not forgive your sins." Like I said before we're asking God for (1) present-tense and (2) conditional forgiveness.

From a Lutheran and Calvinist perspective, we already have total and unconditional forgiveness from the past, so we'd be asking God for less than we currently possess as justified Christians.  In other words, we'd be asking Him to take away some of our forgiveness, and to add a new condition in to what was previously unconditional.  From that perspective, the Lord's Prayer would be a spiritual evil.  But of course, it's not: so the problem must like with the Lutheran and Calvinist understanding of how God's forgiveness operates, rather than with the prayer given us by Jesus. In short, it seems to me that the Protestant notion of forensic justification, in which past, present and future sins are forgiven, cannot be right, given what Christ teaches us about forgiveness, and given the Prayer He leaves us with.