* treatment of women as property
* indentured servitude
* colonialism in the name of "civilizing the savages"
* criminalization of miscegenation
These are things that people pretty much don't argue in favor of in modern America. Granted, there are enormous debates over how much discrimination remains based on gender or race. But very few people will argue that discrimination on those grounds is good. In other areas (like sexual orientation or discrimination against those who are not cisgendered), the debate is more vehement. The trend line is towards acceptance but we're not there yet.
Sometimes I wonder what's next. In two or three hundred years, what will humanity be looking back on and saying "How could those 21st century Americans commonly accept something so awful, so abominable, as that"? Not something that we're really debating right now, but something that most people don't even think about. Something that's just the background of our lives, just the way things are and always have been.
Some of my candidates:
* Animal rights: maybe in 2310 "pet ownership" will seem as cruel and inhuman as "slave ownership" today.
* Employment: "employee" will be considered a step up from "indentured servant" -- "It's not as bad as slavery, of course, but still wrong".
* Children's rights: all current forms of disciplining children will be regarded as child abuse.
These aren't things that I actually think are horrible, mind you. I'm just trying to imagine what things I could be terribly wrong about, just as I consider many things people in 1710 took for granted as "part of the natural order" to be terribly wrong. And of course, there are fringe groups on these issues already: PETA, Communists, "unparenting" in its more radical forms.
What do you think that you might be wrong about?