Many New Testament scholars have observed that the conception of the resurrection body implied in 1 Corinthians 15 clashes so violently with that presupposed in the gospels that the latter must be dismissed as secondary embellishments, especially as 1 Corinthians predates the gospels.
I do not expect that the mere fact that I was once an evangelical apologist and now see things differently should itself count as evidence that I must be right. That would be the genetic fallacy. It would be just as erroneous to think that John Rankin must be right in having embraced evangelical Christianity since he had once been an agnostic Unitarian and repudiated it for the Christian faith.
"Heresy," by the way, simply means "choice." It came to mean "thoughtcrime," implying it was blasphemy to presume to choose your own belief instead of swallowing what the bishops spoonfed you.
The Koran was assembled from a variety of prior Hagarene texts (hence the contradictions re Jesus' death) in order to provide the Moses-like Muhammad with a Torah of his own.
I suspect that, though Craig indulges in a bit of wishful thinking, playing taps for various critical approaches still quite far from death's door, he may well be correct that New Testament scholarship is more conservative than it once was. This has more than he admits to do with which denominations can afford to train the most students, hire more faculty, and send more members to the SBL.
The very admission of the need to harmonize is an admission that the burden of proof is on the narratives, not on those who doubt them. What harmonizing shows is that despite appearances, the texts still might be true.