So this is a really difficult question to answer because comparing one extremely horrible thing to another very horrible thing doesn’t add much to the discussion. However, I do think that it is useful to understand what make European chattel slavery unique in a long historical context. This might give you a way of talking constructively with your parents and explain your thoughts.

Europeans came to the Americas and saw that they could grow things there, products like tobacco, sugar, rice and most infamously cotton. However, such crops require incredibly unpleasant, backbreaking work to produce. To cultivate such products with free labour would require very high wages, so high as to make producing it uneconomical. Unfree labour, however, is cheap. This is the base of African slavery. So what makes American slavery unique? After all the Romans had huge slave populations to work the latifundia of Italy and Sicily. The difference is that Europeans used race as the basis of a political and economic hierarchy to create a particularly brutal form of labour discipline. Race as an ideology was an essential tool for separating people into distinctive groups which could then be exploited for labour. It also allowed to keep that labour in place for successive generations – through laws like the one drop rule. Race and slavery were intimately bound together as an intertwining system of exploitation intended to keep slaves on the plantation in perpetuity. Further, such discipline was systematised and backed up by the financial power and institutional might of the modern(ish, depending on when you ask) state. Race slavery in the Americas acquired a uniformity and totality that slaveries in other times and places could never hope to accomplish.

So, to turn to other slaveries. I’m sure that someone with more knowledge of Rome, China, the near East or elsewhere will come in with wonderful answers on those areas, but I’m an Africanist so I will talk about what I know, the Kuba people of southern Congo. I don’t want to present Kuba slavery as something benign, it wasn’t pleasant at all if you were caught up in it. However, Kuba slavery was much more diverse than its equivalent in the Americas and included many different gradations of freedom and unfreedom. Most Kuba slaves were just peasants who were legally called “slave” but in reality only had to pay an extra tax every year. As a disinterested observer passing through you might not even notice the difference between a slave village and a free one a kilometre further down the road. There were “pawn wives.” Women whose families were in debt who had literally pawned them to the creditor. The woman was a slave and had to work in the creditors house, but her family retained the option to buy her back. Further, any children that she had were free and considered part of her parents family and tribe rather than the owners. Her status as a slave could not pass through blood. There were some slaves who were held as property like American slaves but these were relatively rare. These tended to be prisoners of war or people who had lost all clan connections. They might be freed but continued to have obligations to their masters afterwards – somewhat analogous to how Roman freedmen generally became the clients of their former masters after manumission. Their children as well continued to be semi free but their grandchildren would be members of the extended village in good standing. Finally, there were people who might even seek out slavery for career advancement. The Kuba king’s messengers and lieutenants were all slaves. Such men, while being “slaves of the king” were in reality much more powerful than free chiefs of villages, could accrue significant wealth and even own slaves of their own. The result was a much more variegated vision of slavery which functioned more like a class system than a binary of slave/free.

It’s also worth it to generalise out and think about the link between slavery and the economic and political structures which it rests on. Slavery in the Americas is a system of labour which emerges and contributes to an increasingly global economy based on the cheap production and movement of raw goods. It’s therefore not really slavery which is unique, but rather that modern mode of production. It’s very interesting to look at other forms of unfree labour during the 19th century which do not bear the name slavery but carry many of its characteristics. Think perhaps of the Coolie’s in South East Asia or Poles labouring on East Prussian sugar beet farms. We should possibly ask therefore, what it is about the economy which Europeans built between 1750 (ish) to 1914 (ish) which required such a degree of racialised stratification and unfree work to function.

If you want to read more about racial ideology and its link to economic exploitation I would urge you to check out Alabama in Africa by Andrew Zimmerman. The book itself is about the exportation of Southern plantation agriculture to Africa via Booker T. Washington, but the introduction is one of the clearest theoretical explanations of race and labour that I have ever read. For the Kuba materials check out the Children of Woot by Jan Vansina, although it’s a pretty rare book if you don’t have access to an academic library. For the global picture, Chris Bayly’s Birth of the Modern World is basically the Bible for understanding the transformation of the world in the 19th century. It's a bit old now but no one I have ever read has rivalled it for its synthetic character. Finally, pick up Sven Beckert's Cotton: A Global History. It'll give you all the detail about the 19th century cotton economy.