I read the article. It is fairly general, which makes it hard to respond. I need a specific claim in order to be able to respond. Ehrman’s general complaint is that Christians “look back” at the Old Testament in order to find messianic prophecies. My response is this: Of course they do! What else could they do? Look forward? Jesus himself read the Old Testament and, like he said himself, he was aware that he must fulfill all the prophecies about the Messiah (Luke 24:44). This charge that Christians are abusing the Old Testament because they are looking back (which, by definition is the only thing they could do!) at it is a non sequitur and an attempt to confuse the issue.
Ehrman would do all of us a favor if he would ask the right question which is this: Are Christians taking Old Testament passages out of context, forcing scriptures that have nothing to do with the Messiah to become “messianic?” This is a valid question. What we can do is we can ask whether a particular proposed prophecy is fairly certainly messianic by a reasonable analysis. What is the criterion? A possible criterion is that it would be a passage that the Jews themselves saw as messianic before Jesus came. Or it could be passages that common sense tells us appears to be about a messianic figure. By this standard, some of the passages which Christians claim as messianic would not pass the test. That does not mean that they are not messianic, and that God did not put them there as an anticipation of the Messiah, but just that we can be willing to limit ourselves at the first go to ones which are fairly obviously messianic.
Passages which would make this cut, in my opinion, are Micah 5:2, Zechariah 9:9, Isaiah 9:1-6, Psalm 110:4, Isaiah 11:1, Daniel 9:24-25, Deuteronomy 18:17-20 and Isaiah 53. I could certainly add to this list, but these passages are ones I would consider fairly obviously messianic. Of course, Ehrman wants us to take Isaiah 53 off the list, but that is because he really does not like how wonderfully and perfectly it fits Jesus, and how convincing it is, not only to Christians, but even to many outside of Christianity. He may cry foul all he wants, but there were significant Jewish voices calling Isaiah 53 messianic before Christ (although he denies this), including the Qumran community and others. Ehrman desperately wants to exclude this passage, but any passage which mentions a person who brought us peace, who takes on all our iniquity, who bears our suffering, who is an offering for sin, who will justify many, and who will bear the sin of many has GOT to be messianic. Sorry, Ehrman, but you are begging the question on that one.
But, by the standard above, a number of passages which I personally am convinced are messianic and which point to Jesus would be ruled out. This would include Psalm 22:16-18, Hoseah 11:1, Zechariah 11:12-13, and Isaiah 7:14. Other classic messianic passages could be added to this list as well. These are passages with information which fits well with Jesus, but which, objectively, are not obviously messianic, and are only seen that way because we can look at the life of Jesus and look back to the Old Testament and see the parallels.
The list of passages which are clearly messianic, and which do not require “looking back” to identify them as such are more than enough to create a fantastically strong case that Jesus is the Messiah, especially because several of them involved things over which Jesus had no control (Micah 5:2, Isaiah 9:1-6, and parts of Isaiah 53). If we have established that Jesus is indeed the Messiah (and from these prophecies we have, and he is) then Christians are fully justified in turning to the Old Testament to find other prophecies which the Jews did not, and perhaps even could not have identified as messianic after the fact. Having established that Jesus fulfilled all the former list in fantastic and specific ways, it is absolutely legitimate for Christians to add the second group to the list of messianic passages. For example, having established that Jesus clearly fulfilled Micah 5:2 by being born in Bethlehem, and Zechariah 9:9 by riding into Jerusalem as king on a donkey, and having been pierced for our transgressions (Isaiah 53), it is only reasonable to also notice that Jesus was called out of Egypt, was betrayed for 30 pieces of silver and was pierced by hands and feet.
Ehrman does not make a distinction between before-the-fact and after-the-fact messianic prophecies, because he has ruled out the very idea of biblical inspiration before he ever looked at any passage of Scripture. He makes excuses for ignoring the first list, and then, a priori, rules out the second list. It is not surprising what he is willing to ignore, based on this, which includes what I am admitting are after-the-fact messianic prophecies. There is no legitimate reason to rule out Zechariah 11:12-13 as a messianic passage, even if it is not “obviously so” to Jews who have not yet met their Messiah. If Jesus is the Anointed One, and he is, then it is not at all a stretch to imagine that God prophesied his coming in more subtle ways, such as putting the prophecy into a mournful cry of David (Psalm 22:14-16) which only clearly becomes Messianic after Jesus was crucified.