Throughout all of human history there have been people, and not just slaves, who viewed slavery as wrong and immoral. They may have been a minority in many societies but they existed.

Racism was not "invented" by "modern slavery", it has always been there.

Being exploited at a low wage, zero benefits job is not "slavery". You comment is analagous to the cries of "genocide" when a protester gets injured or arrested. Words like slavery and genocide have specific meanings and should not be dumbed down because that diminishes the true horror experienced by those who actually suffered from them. I have seen a number of rightwing memes claiming Irish people were enslaved in early America, when in fact the had signed up for indentured servitude. This required them to work for someone for a specific number of years, but they were not slaves. The still had legal rights. If they died before they finished there contracts their families were not bound by it. Many did this to pay their passage to the New World.