"Sparta" is the name of the principal city of the city-state of Lacedaemon, which comprised the regions of Laconia and Messinia in the Peloponnese. The inhabitants of the city of Sparta are in ancient sources referred to as Lacedaemones ("Λακεδαίμονες") and are the people we, in the modern day, know as as Spartans or Spartiates ("Σπαρτιάται").
The people inhabiting the greater area of the Lacedeamonian city-state, the inhabitants of the settlements in Laconia and Messinia, were never referred to in any ancient text as "Spartans" or "Lacedaemones" and they were only referred to, to the extent they were ever mentioned, as "helots" ("είλωται") or, simply, as the Spartans' slaves. Any reference to those people as "Spartans", let alone "Lacedaemones" is a modern invention and only serves to deepen the confusion I highlight here. In fact, I am only aware of a single modern "source" that commits this confusing error: the blog post linked above. If we were to give those people a modern name devoid of political connotations, that would be "Lacones" ("Λάκωναι") or "Messinians" ("Μεσσηνοί"), the inhabitants of the regions of Laconia and Messinia.
So it makes no sense to say that "Sparta" was "80% enslaved people" or the other errors committed in the linked article. It might make sense to say that "Laconia and Messinia (resp. Lacedaemon) was 80% enslaved people", although that would greatly weaken the intended invective against Spartans. It would certainly make sense to point out that Spartans, i.e. the inhabitants of the city of Sparta, had a huge number of slaves in proportion both to their own numbers and in comparison to the number of slaves of other Greek city-states of the same historical period(s), but again that would not be a proper attack on the myth of Sparta, which is what is intended. Of course it makes every sense to point out the cruelty of Spartans, but in that case, if we call the helots "Spartans", also, the confusion only deepens.
All such nuance is left out of the article linked above which makes it very, very misleading and confuses people who are used to getting their knowledge of history from second- third- and further- hand accounts, like the one in the linked article, or the movie 300, etc. Unfortunately once something is elevated to mythical status there is nothing more profitable than to tear it down, even if this tearing down is based on the same poor knowledge of history that allowed it to be elevated in the first place.