You have to be more objective. Historians realize it was a product of their time, but it's importance was tantamount in an agricultural driven society in which nation-states required even more resources as their borders expanded rapidly. Slavery is neither good, nor necessarily bad, and we can't make those types of judgments for people thousands of years ago for whom it was a part of life.
The Trans-Atlantic slave trade is much different than the slaves accumulated by the Romans for instance. Many slaves in Rome's had rights. Many we're teachers, home-owners, participants in society, but beholden to a master, but for no longer than 12 years.
In the world of Fallout, it's interesting to see how many of our ethics and moralities in a somewhat stable society hold up when society is no more. I would say that's the most important question. Will we cease to be who we are when everything falls apart? What are rights? What is morality? According to the law of nature, there is no right nor morality. We're the Legion acting on behalf of nature, in a sense, stripping away the weak and decadent, and creating something new and stable?