Also re: slavery I would agree with your characterization of most defenses of (American) slavery. The next natural question follows: what to do about it? Have you heard of the 1835 postcard campaign? https://www.econtalk.org/munger-on-slavery-and-racism/

In that case, loudly and publicly condemning groups of people tends to cause them to circle the wagons and double down on their positions. I think there's a lesson for today there as well.