From the Helot's point of view that's just so much BS. The Spartans kept the Helots as slaves. The Celt's kept the Germans as slaves, albeit in tribal groups, but in slavery nonetheless.
The Iriquois understood the concept quite well having been the slaves of the Algonquins earlier. Their histories, when reduced to writing, all begin, "when we were slaves". So, too with the Jews!
Slavery is such a universal situation with humanity that anyone who denies that it existed at one time or the other among any group of humans is simply not to be trusted.
BTW, one of the little stories in the ancient Briton stories of Arthur has him showing Christian piety and kindness by hunting down another man's slave and returning the slave to the master.
Like I said, universal!
As someone who studied the matter I can tell you first hand the Helots DID NOT view themselves as slaves nor did the Spartans view them as such. The Helots were well aware of slavery in Greece. The slave markets were everywhere in Greece. The Helots knew they were oppressed but they never viewed themselves as slaves. All forms of opression are not slavery.
Your lying to try to make everyone else look almost as evil as the Musli is not fooling anyone.