Why is the Kentaur Chiron Regarded as the Tutor of Achilles?

Above, we see two Kentaurs, half-men/half-horses, pounding a man into the ground with a boulder. Who is this man to the Greeks? Why would Greek artists spend years of work sculpting such a scene?
Greek artists sculpted Kentaurs on the temple of Poseidon south of Athens, on the temple of Apollo at Bassae, on Athenas templethe Parthenon, on the temple of Zeus at Olympia, and on many other temples including the west frieze of the temple of Hephaistos in Athens, pictured in part, above. Kentaurs appear often on Greek vase paintings.
The standard explanation is that the battle between Greeks and Kentaurs
represents the struggle between civilization and barbarism. While there
is a grain of truth in this, the facts just dont fit into such
a general theory. Why, if Kentaurs represent barbaric men, is the Kentaur
Chiron highly regarded as the tutor of the famous warrior Achilles?
Consider this: eighteen of the thirty-two metopes on the south side
of the Parthenon depicted Kentaurs fighting men; and while the battle
appears even on four of the metopes, on at least ten of them, the Kentaurs
are defeating the men. Why would a temple designed, in part, to showcase
the glory of Athens, feature a defeat at the hands of barbarians? And
what about the scene above?
Well need to generously engage our skeptiosity in order to grasp
what the Greeks were trying to tell us through their ubiquitous depictions
of these strange creatures.
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