Roman slaves, including in Herculaneum, were chattel; they could be bought and sold, and their children were born into slavery. Their owners could break up their marriages with impunity simply by selling them or their spouse to a different household.
Aisopos was also a chattel slave, but he lived 600 years earlier, in a very different culture from that of Herculaneum; consider the difference between your own circumstances and the circumstances of domestic servants 600 years ago in Russia.
Herculaneum did not have very much social mobility; it was a society with much more persistent stratification than our own. Half of Herculaneum's citizens (the most privileged 20%) were freedmen, but most of the wealthy citizens were the great-grandchildren of wealthy citizens, and the great majority of people born enslaved died in slavery. Freedmen and often even their children were ineligible for most political offices. Throughout Italy, 80% of decurions had no slave ancestry at all, any number of generations back. (I'm not sure what the number was in Herculaneum.)
To liberals, enslaving someone is itself ill treatment and abuse, because we consider freedom to be the birthright of every human being, and its denial to amount to ill treatment. So we consider the idea of slavery without ill treatment and abuse to be a contradiction in terms. Even if a slave is not being beaten, raped, berated, or worked to death in a mine, they are being deprived of many of the most precious things in life by the very nature of slavery.
Aisopos was also a chattel slave, but he lived 600 years earlier, in a very different culture from that of Herculaneum; consider the difference between your own circumstances and the circumstances of domestic servants 600 years ago in Russia.
Herculaneum did not have very much social mobility; it was a society with much more persistent stratification than our own. Half of Herculaneum's citizens (the most privileged 20%) were freedmen, but most of the wealthy citizens were the great-grandchildren of wealthy citizens, and the great majority of people born enslaved died in slavery. Freedmen and often even their children were ineligible for most political offices. Throughout Italy, 80% of decurions had no slave ancestry at all, any number of generations back. (I'm not sure what the number was in Herculaneum.)
https://www.jstor.org/stable/4436383
To liberals, enslaving someone is itself ill treatment and abuse, because we consider freedom to be the birthright of every human being, and its denial to amount to ill treatment. So we consider the idea of slavery without ill treatment and abuse to be a contradiction in terms. Even if a slave is not being beaten, raped, berated, or worked to death in a mine, they are being deprived of many of the most precious things in life by the very nature of slavery.