The basic great error is that Doherty held still to an earthly image of the crucifixion for Paul, even if he placed that image in outer space (where Doherty is right).
Really, when Paul says :
O foolish Galatians! Who has bewitched you that you should not obey the truth, before whose eyes Jesus Christ was clearly portrayed among you as crucified?
(Galatians 3:1)
the folly of which the Galatians suffer, is the same "foolishness" of which in general all the not-pauline Gentiles suffer:
The belief that the crucifixion was an earthly crucifixion, beyond where it is placed.
For example, Doherty is still victim of a similar belief, even if he placed the crucifixion in outer space. When Doherty says that a tree and nails could be still in outer space, he is simply saying that the crucifixion in outer space could be conceived as an earthly image of a crucifixion.
Well: this is "foolishness" for Paul. This is precisely the "scandal" of the cross, for Paul.
To be compelled to have an earthly image of the crucifixion, by using earthly images to represent it.
This is the reason the Apostle rejects the use of the "wisdom and eloquence, lest the cross of Christ be emptied of its power ":
For Christ did not send me to baptize, but to preach the gospel—not with wisdom and eloquence, lest the cross of Christ be emptied of its power.
For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God.
For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God.
(1 Cor 1:17-18)
When the crucifixion is "emptied of its power"? When you describe it as an earthly crucifixion, by using, to explain it, the curse of hanging of Deuteronomy, the image of Attis hanged, or an example among many of the servile supplicium.
The Galatians are "fools" because Paul was compelled to use earthly images (even by using the OT scriptures) to evoke in them (a not civilized people, differently from the Corinthians) the image of the crucifixion of Christ.
Under this light, we can understand who are the "enemies of the cross of Christ":
Philippians 3:18-19
For, as I have often told you before and now tell you again even with tears, many live as enemies of the cross of Christ. Their destiny is destruction, their god is their stomach, and their glory is in their shame. Their mind is set on earthly things.
They are all the people who interpret the crucifixion by using an earthly image (of a servile supplicium), even if they believe in the essential deity of the victim. Even if they place the crucifixion in outer space. They are people who materialize the crucifixion.
Hence, the "scandal" of the cross of which Paul talks, can't be used at all as evidence of historicity. At contrary, it is evidence of the celestial crucifixion defended by Paul: the cosmic crucifixion of a giant-like Jesus in outer space.
The drama of the Apostle is that all the people around to him, insofar the community increased, had more and more need of earthly images to represent to his own eyes this cosmic crucifixion of a giant-like Jesus. The idea of the servile supplicium was an effect, not the cause, of the unavoidable materialization of the belief.