Specifically on the basic level of slavery. Most people today believe that slavery is a bad thing and that no one should be a slave, and seeing all human beings as, well, human beings, mostly. We have made progress toward the libertarian society that I and other consent radicals want. I think that this most basic thing is pretty much irrefutable.

This has coincided also with massive economic growth since the gradual abolition of slavery in the 1800s, and I think there is some significant bidirectional causality there. It is much harder for people to be complacent with there being slaves everywhere when they have enough comforts to now think about other people. Slavery is also inefficient and unsustainable, and its removal brings more profits to those who do not construct power structures to keep people enslaved. These power structures, incidentally, can only be constructed at great expense, usually with other people's money, as slavery loses money when protection of that alleged right is left up to individuals. Once it is no longer supported by the state, it is almost universally eradicated.