When the evidence is uncomfortable, if you can't trim it, cast doubt on it.
Here (italics mine):
Matthew blends in with Jesus’ mission charge to the twelve disciples certain prophecies about the end times, about the coming of the Son of Man. So you get a verse like Matthew 10:23, “When they persecute you in one town, flee to the next; for truly, I say to you, you will not have gone through all the towns of Israel, before the Son of man comes.” Originally this was probably a saying about the end of the world, the coming of the Son of Man; but here Matthew has woven it into this mission discourse to the Twelve. ... [B]y putting this saying in this context, Matthew makes it sound as if Jesus is saying to the twelve disciples, “Before you have gone through all the towns of the Israel, the coming of the Son of Man will occur.”
This is a perfect illustration of my contention. If Matthew 10:23 did not mean that the Son of Man was going to come again before the mission of the Twelve was over, there is no reason to think that Matthew 24:34 means that the Son of Man is going to come again within the first generation. We can’t be sure how this saying was originally given or what its context was. ...
But now look at how Matthew handles this verse in Matthew 16:28. Here Matthew, telling of this same event, rewords it. Remember, they didn’t have quotation marks. This is paraphrased. Here is Matthew’s way of putting it: “Truly, I say to you, there are some standing here who will not taste death before they see the Son of man coming in his kingdom.” Now that does [italics original] sound as if they are going to see the return of the Son of Man in their own lifetime! But we know that Matthew is paraphrasing this passage in Mark 9:1, which doesn’t really say that. Matthew is passing it on in a somewhat different way. This case again illustrates my point. These sayings may have a very different meaning in their original context. Someone who only knew Matthew 16:28 might well think that Jesus is saying, “There are people here who will not die before they see my parousia,” but when you read Mark 9:1, that is not at all obvious.
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At least with Albert Schweitzer's interpretation, Matthew and Mark are allowed to stand as reliable presentations of (failed) apocalyptic.
So who's the "conservative", William Lane Craig, or Albert Schweitzer?