It was not merely that the leisure which enabled a citizen to devote himself to the Republic was dependent upon the forced labour of others. Slaves also satisfied a subtler, more baneful need. ‘Gain cannot be made without loss to someone else’: so every Roman took for granted.
All status was relative.
What value would freedom have in a world where everyone was free?
Even the poorest citizen could know himself to be immeasurably the superior of even the best-treated slave. Death was preferable to a life without liberty: so the entire history of the Republic had gloriously served to prove.
If a man permitted himself to be enslaved, then he thoroughly deserved his fate. Such was the harsh logic that prevented anyone from even questioning the cruelties the slaves suffered, let alone the legitimacy of slavery itself.
It was a logic that slaves accepted too. No one ever objected to the hierarchy of free and un-free, merely his own position within it. What the rebels wanted was not to destroy slavery as an institution, but to win the privileges of their former masters.
So it was that they would sometimes force their Roman prisoners to fight as gladiators: ‘Those who had once been the spectacle became the spectators.”
Only Spartacus himself appears to have fought for a genuine ideal.