Why did Jesus kill the Pigs?

JESUS CASTS DEVILS OUT OF THE SWINE: TRUTH OR SUN MYTH RETOLD?
Williams Harwood has some interesting things to say about this teaching in light of historical facts. "Since the fall of the city a few months earlier [in 70 C.E.], Jerusalem had been occupied by the Roman Tenth Legion [X Fretensis], whose emblem was a pig. Mark's reference to about two thousand pigs, the size of the occupying Legion, combined with his blatant designation of the evil beings as Legion, left no doubt in Jewish minds that the pigs in the fable represented the army of occupation. Mark's fable in effect promised that the messiah, when he returned, would drive the Romans into the sea as he had earlier driven their four-legged surrogates." - William Harwood, Mythologies Last Gods: Yahweh and Jesus. Unlike Gerasa, Gadara was the scene of a a great massacre of Jewish rebels by the Roman troops in 69 C.E. Like the pigs, the fleeing rebels were driven into the water. "Vespasian sent Placidus with 500 horse and 3000 foot to pursue those who had fled from Gadara..." (Sn 4) "Placidus, relying on his cavalry and emboldened by his previous success, pursued the Gadarenes, killing all whom he overtook, as far as the Jordan. Having driven the whole multitude up to the river, where they were blocked by the stream, which being swollen by the rain was unfordable, he drew up his troops in line opposite them. Necessity goaded them to battle, flight being impossible... Fifteen thousand perished by the enemy's hands, while the number of those who were driven to fling themselves into the Jordan was incalculable; about two thousand two hundred were captured..." (Sn 5) - Flavius Josephus, War of the Jews, Bk IV, Ch 7. Josephus reports that as a result of the battle "the Jordan was choked with dead", and "even the [Dead Sea] was filled with bodies." (War of the Jews, Bk IV, Ch 7 Sn 6).