[rsynnott]

> Yet something about Sparta seemed worse.

Very few other slave societies _had kids ritualistically kill the slaves as part of their education_ (there's maybe some wiggle room on whether this actually happened or was mythical, but it's _definitely_ part of the popular view), so there's that.

Sparta was also an oddity just in the sheer size of the slave class; under 5% of the population was fully free. Few if any other slave societies had that sort of ratio.

> That is, did the Spartan ruling class look down on the helots as not just inferior but alien?

Yes; they were 'foreigners' (they were originally, at least mythically, inhabitants of a neighboring city state). They also had a separate discriminated class for Spartans who'd been stripped of civil rights; these weren't viewed as the same.