Jesus seems to function as a servant to God the Father more than anything else. If the Angel of the Lord is interpreted as being the pre-incarnate Christ, he certainly also seems to have also taken a far harder edge in his pre-incarnate appearances.
If we were to cherrypick portions of the Bible in the same manner that many Christians do, we might very well use this verse to claim that Jesus was never intended to forgive or pardon transgressions. That verse could certainly be exaggerated as much as they exaggerate other portions of the Bible.
I agree that Christ sometimes pops up in the OT as an 'Angel of the Lord' but that is not to say that every 'Angel of the Lord' in the OT is Christ Himself. Do you have any evidence that this one is?
I've never seen where Christian theologians suspect that it was a Christophany.