There is somewhat of an ugly undercurrent of "might makes right". With Greek myth, heroes being successful typically meant they had the favour of one or more of the gods, and this attitude seems to have carried over into Christendom: that if one was successful, clearly they had the favour of capital G God, and filtered through Christian morality, that must mean they are inherently righteous, right? Given Monmoth and de Troyes writings were during the time of the Crusades, I suppose that's to be expected.
That’s quite right, and more besides. To some degree, tales of chivalry were knights telling each other that they were good people really, that everything they did - the murder, the looting, the brutality, the other terrible stuff - was justified, normal, and blessed by God. They were the enforcers of a terribly unequal, oppressive, precarious, sexist, classist, racist society. Do we want to replicate those things in our games? Well, that’s up to the table. The same can be said of many games set in the past, such as games set in Imperial Rome or Sengoku Japan. We can choose to run games set in versions of those societies that are more equal and kind if we wish - female knights are common, no chattel slavery, the rule of law for all.
This is a bit like what T H White tries to do in The Once and Future King, now nearly a century old. His Arthur is enlightened by the standards of 20th century England and is thus appalled by Might Makes Right; he determines that his reign will be marked by Right Makes Might. So he speed runs medieval legal reforms (courts, magistrates, etc) and distracts his disgruntled nobles with the illusion of equality (the Round Table) and as many magical quests and adventures as he can find. It all comes crashing down, of course, but at least he tried.
And to this day we retcon what Camelot and Arthur mean to us. Here’s an exchange from Justice League Unlimited, of all things:
Shining Knight, the last survivor of Camelot in the modern world: Do your worst. I'll not let you harm another.
General Wade Eiling, now the Shaggy Man: I do what I do in service to my country.
SK: Once at the word of my lord, King Arthur, I was ordered to lay waste to an entire village. I knew my king's heart could not be so unjust. So I spared them all.
WE: Then you're a lousy soldier.
SK (sighs): There it is, the creeping moral decay of the past thousand years! Arthur thanked me, oaf. Had I been wrong, I would have handed over my sword and left the court in shame.
The above exchange would probably have been unrecognisable and farcical to many medieval writers.
