I think a good litmus test for an argument is whether you approve of things that such a view can be logically extrapolated to imply. And here you must certainly realize that your argument can be used, and indeed
is used, to justify the most heinous of ideologies. There are millions of people, and nations, that still believe as a moral absolute that a person ought be killed for behaviors such as apostasy, homosexuality, blasphemy, atheism, sorcery, adultery, and so on. And of course these individuals cannot be logically moved from their position since they simply double down on their moral self assuredness. Ultimately, moral absolutes are best left to religion, and religion is best left to mythology.
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Even for things like slavery, most people look through a revisionist lens of times, both past and present. This [1] article from WaPo states some 30 million today are enslaved -- more than at any other time in history. It's certainly sensationalized, but only in magnitude - not reality. The more important takeaway from the article is the locations of where slavery is most prominent today. And it's in countries that failed to economically and technologically evolve.
Something often ignored in favor of softer factors for the ending of slavery is is this [2]. That extensively sourced article goes into the price of a slave in the US in the mid 19th century. In price terms relative to how much each individual earned per year, a slave would cost more than $200,000 in modern day dollars -- a single slave cost as much as a house did. And that's before you get into housing, feeding, and ensuring the good health of your slave. You'll find abolitionists moralistically arguing for literally thousands of years, and even 'Lincolns' dating back to as early as 7AD (China in that case).
The thing you won't find is slavery persisting in areas where it became uneconomical. And an even more serendipitous occurrence is that this was happening at the very time that the industrial revolution was driving urbanization creating a massive pool of low wage labor. And on top of this all rising productivity also meant that paying somebody a wage was no longer as burdensome a cost to bear. These factors are arguably what genuinely meant slavery in the United States was finally brought to an effective end. And similarly the reasons it continues to 'thrive' in other areas today is not for lack of moralistic arguments, or even laws against it, but simply because of the economic factors are, for various reasons, not yet in play.
[1] - https://www.washingtonpost.com/news/worldviews/wp/2013/10/17...
[2] - https://www.measuringworth.com/slavery.php