During the whole debate Dr. Craig emphasized the reasons for believing in the resurrection as an historical event -- the certainty of Jesus' death and burial; the empty tomb; the multiple, bodily post-resurrection appearances (not visions); and the counter-intuitive origin of the belief in his coming back from the dead.
I expected he would answer the audience's question from the same chapter that he often quoted in his arguments and rebuttals: 1 Corinthians 15:1-2, "Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand, by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain" (NASB, my emphasis).
But I was disappointed. He said it was up to God to decide who was a Christian and who wasn't. Well, true enough . . . maybe he wanted to avoid personal attacks in the debate. But there's enough information in Scripture for us to discern when a person is denying the faith, and Spong certainly does in his numerous writings. That's a matter of public record. And he opposed the gospel in that debate as well.
The retired Episcopal bishop from North Carolina denies God's personal existence, the virgin conception of Jesus, the substitutionary atonement, the bodily resurrection of Christ, His miracles, and the authority of the Bible's first-hand witnesses. Although he calls himself a Christian, he has certainly redefined the term. By the apostle Paul's definition, Spong and others who stand in his Enlightenment tradition have no right to use this description for themselves, but would be far more honest to call themselves what they are -- existentialists, mystics or rationalists. Spong says the gospels were put together long after AD 30 and therefore express in mythological form the thoughts of second century Christians about what Jesus was to them. But it would be far more accurate to say that the liberal theology of Tillich and James Robinson (Spong's own mentors) represents the opinions of modern men about things which they would rather deny. The gospel writers reported and defended what they themselves had seen and heard, along with other first-hand testimony. Spong reports and defends what Western philosophers have dreamed up and marketed as a cheap imitation of the apostolic tradition.
Rather than hide behind a false label, how much better to make things clear -- the gospel has specific content to be believed. Redefining the terms and believing something very different from what Christ and the first disciples taught is immoral: it lies about the apostolic witnesses, tells people they are saved when they are not, and leaves Christians in their sins (1 Corinthians 1512-20).
How much better to take seriously what Jesus said to the disciples on the road to Emmaus: "O foolish men and slow of heart to believe in all that the prophets have spoken! Was it not necessary for the Christ to suffer these things and to enter into His glory?" (NASB Luke 24:25-26).