Freedom as a philosophical principle is a modern concept, probably younger than the 150 years since the American Civil War, and certainly not more than two millennia old as would be necessary for the historical Spartacus to be seeking it. The American Revolutionaries talked "freedom" but that was not a sufficiently deep nor profound philosophical principle for them to give up their slaves. That same web site also pointed out how popular Spartacus is with the Marxists, as a liberator of the proletariat. Sounds a lot like the movie theme. At least the (first-generation) Marxists were more committed to their principles than the modern armchair philosophers and movie makers, who mostly don't believe anything is worth dying for.
But the ethical idea in this film that got my attention was sexual.
Everything in America today is sexualized. Kevin Costner's character in
Dances
With Wolves fornicated with his female supporting character long before
there was a formal marriage relationship. This is true in most modern movies,
but it was less credible in DWW, because almost no non-modern culture would
allow them to do that. In Spartacus, as in BraveHeart, there
was the usual and expected rape of the young maidens by the soldiers (which
even moderns deplore), but like BraveHeart (and unlike other modern
flics), the hero was unwilling to defile his leading lady before marriage.
In Spartacus he actually explained it as a Thracian virtue. Bravo!