Why say that Plato lied? That he was engaged in some devious deception? Maybe he was just wrong.
I believe Plato came up with his false simile the day he was supposed to pour the olive oil in the new jug, but instead drank all the wine in his personal closet.
I'm not going to give the author's site a hit, but I will point out that in Plato's Republic he explicitly introduces the so-called "Noble Lie" to justify rule by his Philosopher Kings.
The Republic was all about being ruled by the elite (philo. king) and he argued for a slave state...You do what the king (who knows more than you) says you do.......
Decimon:
He knew what he was doing. He was a sneaky SOB who intended to discourage any attempts at future republics.