> No, the comparison to an APC (armored personnel carrier) is apt- knights were armored enough to be nearly invulnerable to the weaponry a peasant would have access to.

No. A knight prone on the ground was very easy to kill very quickly - just stick a dagger through the visor. There is nothing comparable a civilian today can do to an APC.

Additionally, a single knight on a horse was not that hard to take down using relatively easily-available polearms, at least to a group of peasants. It doesn't scale down linearly - 40:9000 is a very different matter than 1:200, because a charge of 40 mounted knights is still inescapable death to the part of the enemy force they're charging at. A single knight would be much less terrifying even to a relatively group of peasants.