(The following is from “Jesus: A Revolutionary Biography”, John Dominic Crossan, pages 35-38)
Antipas's execution of John cannot be explained by a simple appeal to Mark 6:17-29, even if one took that marvelous fiction as historical fact. ... [Mark 6:17-29 cited] ...
Mark's account is best seen as his own creation, allowing him to emphasize certain parallels between the fate of John and Jesus, especially how both were put to death at the insistence of others by a reluctant and almost guiltless civil authority— Antipas for one, Pilate for the other. In life, death, and even burial by disciples, John is, for Mark, the precursor of Jesus. And, probably, he was deliberately recalling an earlier and well-known Mediterranean horror story. When, in 184 b.c.e., Cato was one of the two official censors at Rome, he had Lucius Quinctius Flaminius expelled from the senate despite his consular rank. His crime is described by the orator Cicero, who died in 43 b.c.e.; again by the historian Livy, who died in 17 c.e.; and finally by the rhetorician Seneca the Elder, who died in 40 c.e. Here is one of the two versions in Livy's history of Rome, Book 39.43:3-4.
At Placentia a notorious woman, with whom Flaminius was desperately in love, had been invited to dinner. There he was boasting to the courtesan, among other things, about his severity in the prosecution of cases and how many persons he had in chains, under sentence, whom he intended to behead. Then the woman, reclining below him, said that she had never seen a person beheaded and was very anxious to behold the sight. Hereupon, he says, the generous lover, ordering one of the wretches to be brought to him, cut off his head with his sword. This deed ... was savage and cruel: in the midst of drinking and feasting, where it was the custom to pour libations to the gods and to pray for blessings, as a spectacle for a shameless harlot, reclining in the bosom of a consul, a human victim sacrificed and bespattering the table with his blood!
The point was not that the man was innocent; he was going to be executed in any case. But it should still not be done just to please a mistress, and not at a banquet. The story was clearly a well-known example of how not to exercise power. Mark's creation intends, most likely, to recall that classic model.
Even if one took John's criticism of Antipas's marital rearrangements as fact, it would hardly be warrant for execution. Some more serious threat must have motivated Antipas's action. One could, indeed, almost guess what that threat must have been, since Josephus gets most oblique, devious, and defensive whenever Jewish messianism or apocalypticism is in question. It would hardly do, after all, to show too clearly that what Josephus had applied to the Roman emperor Vespasian could also be applied by others to anti-Roman Jewish patriots, especially to ones of a class far, far beneath the imperial purple. And it is precisely as an apocalyptic prophet that John appears in the New Testament gospels, although there too one sees a tendency to smother politics in piety and rebellion in religion.
Josephus never mentioned anything about the wilderness or the Jordan in relation to John, and he protested too much that John's baptism was not to remit sins. Mark records wilderness, Jordan, and remission of sins, a contradiction to Josephus that warns us that those elements hang somehow together, that their omission served Josephan interests. ... Here is Mark 1:4-5:
John the baptizer appeared in the wilderness, proclaiming a baptism of repentance for the forgiveness of sins. And people from the whole Judean countryside and all the people of Jerusalem were going out to him, and were baptized by him in the river Jordan, confessing their sins.
Geographically that area extends on either side of the southern Jordan Valley. It included most of Antipas's Perean territories and was protected on its southern borders by the palace-fortress of Machaerus.
From another gospel source we even get a sample of one of John's sermons that had, according to Josephus, so aroused those unidentified others. John said, according to the Q Gospel in Matthew 3:7-12 or Luke 3:7-9 and 16b-17:
"You offspring of vipers! Who warned you to flee from the coming fury? Change your ways if you have changed your mind. Don't say, 'We have Abraham as our father.' I am telling you, God can raise up children for Abraham from these stones. Even now the ax is aimed at the root of the trees. Every tree that does not bear good fruit is cut down and thrown into the fire.... I am plunging you in water; but one who is stronger than I is coming, one whose sandals I am not worthy to touch. He will overwhelm you with holy spirit and fire. His winnowing fork is in his hand to clear his threshing floor and gather the wheat into his granary. The chaff he will burn with a fire that no one can put out."
In the present sequence of the gospel narrative, the prophecy of the Coming One refers to Jesus, although, to be sure, it hardly serves as a very good description of Jesus' activity. It is only, however, in John 1:26-31 that the Baptist rephrases his prophecy and then explicitly applies it to Jesus: ... [John 1:26-31 cited] ...
That explicit rephrasing and direct application underlines what is evident in John the Baptist's sermon when it is taken by itself and apart from its present location in the gospel sequence. John was not talking about Jesus at all but rather about the imminent advent of the avenging apocalyptic God. That cataclysmic advent is imagined with two powerful images, behind both of which stands the threat of fire. God as the Coming One is first like a forester with an ax separating good trees from bad and then like a thresher separating grain from chaff. For John's fiery vision there are only two categories, the good and the bad, and the time is very short to decide in which category one intends to live and die.
Exactly what Josephus predictably suppresses about John the Baptist is what we find about him in the gospel stories despite their own rather different theological interests in turning John into the herald of Jesus. John was an apocalyptic preacher announcing, in classical Jewish tradition, the imminent advent of an avenging God and not, like Josephus, the imminent advent of an imperial conqueror.