When you're young you form opinions, often strong ones and good for you if you have opinions formed from your own mind and not just rehashing years of indoctrination via the state education machine.
As you get older you find your opinions can become old fashioned, now at one time the opinions of older people were, like them, listened to and respected even if you disagreed with them.
In the current climate the opinions of the older generation have become vilified from many quarters, sometimes to be dismissed as various isms and ists, we have gone through a sea change of disrespect for the past and the people who in some cases forged the past, but the past is the past, it is what it is and makes us what we are today, if we are wise we learn from it hoping to replicate the best and never to repeat the mistakes.
This is how it should be, but there is one thing those who have strong opinions, which these days tend to detest the thoughts and words from previous generations and make no secret of their hatred, should remember, that in a couple or three decades what went around will come around again and currently right on thoughts and words will be equally derided by the next generation, and so it goes on.
Getting back to slavery, apart from some modern slavers in western lands (generally called human traffickers now though i have a rather different description of them and a better terminal idea of what to do with them),foul specimens that they are, no one currently alive in the western world was anything to do with the foul slavery that went on in those times, they were dark days indeed but it should be remembered that decent men fought and died in struggles and wars to put a stop to slavery.
If you go back far enough you'd find things happened to your own families that were unjust and cruel beyond belief.
What we have to do is make sure this never happens again, personally i think we are on a knife edge of losing our freedoms to a bunch of world owning oligarchs pulling the strings of bought and paid for politicians and media moguls who in turn spread their vision of utopian hell down through a greedy gutless mainstream media.