What about the Verna / Vernae, aka descendents of the original slaves and thus born into slavery? What does honor or being captured have to do with these people?
What about Fathers who sold their underage children into slavery to settle their own debts instead of becoming slaves themselves?
I am sorry but if you are going to pull the historical crap saying modern people can't critique old institutions than you should bring up all the historical crap. Do not be selective for that is just as big of a error of logic (rational and emotional) and is fallacious in its reasoning.
How about how future Roman Emperors such as Augustus prevented the freeing of slaves until the person is the age of 30. This 30 number is even more horrendus when you realize life expectancy was very different in the Roman Empire compared to modern day (Average Life Expectancy aka of a newborn was mid twenties aka 50% of the people would be dead at 25 or prior and 50% would still be alive for every newborn, if you surived to 1 your life expectancy increases and now 50% would be alive and 50% would be dead at 35, if you survived to 20 the 50% mark means you would be dead at the age of 50). Aka it was not very common for you to get your freedom if you were born or sold into slavery as a child for the law forbid you being free and then you needed a master who wants to free you (out of generosity or a recognition of a good deed) or someone who is not you willing to buy your freedom.
You whitewashed a lot of history for the reasons you listed were not even close to all the ways you could become a slave in the roman empire (and the late roman republic). Yes slavery in Rome was complicated, for example you could be free from slavery.
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If you want to understand my original point which I thought was self obvious, people demonize and turn into villains people they have never met and how class is an inherent part of it. And people do not get it, they think they have true rational reasons when they vilify people and call them vile.
In reality this is just accidents of birth, these people we turn into villains (when I say turn into villains I mean with language we identify these people as villains even if the label is not really accurate), these people we call villains are often not despicable, bad people, or even trying to restrict our own attempts at doing good.
Often people which we label villains are just merely people trying living their own lives, trying to feed their own kids and they just seem to live in a place where now they are some form of obstacle such as they have land we want, or people who are not them but are people that are their leaders get them tangled up in a war.
Or people we identify as villains are just accidental bystanders who merely just live in a country where there are crazy terrorists and since we can't figure out who is the real terrorists for unlike comicbooks terrorists do not dress the part where you can easily identify a terrorist vs a non terrorist on site since people on the outside look the same and you can't judge a person's ideology or intentions by how they look on the outside.