We need to enter the conversation willing to be wrong, willing to admit the limits of our own knowledge, willing to reconsider our evidence, sources, and premises. That is self-skepticism.

Arguments for slavery weren't pragmatic or ethical discussions about the realities of slavery; they were assertions about abstract identities (The Slave, The Slave Owner, The Abolitionist) and performances of loyalty to the South. They were demagoguery.

The other argument [about the Iraq War] was about argument itself. It characterized any argument about policy (whether, in fact, Iraq did have weapons of mass destruction and whether regime change could be effected through an invasion) as unnecessary, dithering, disloyal, and possibly even deliberately evil, since the correct course of action was so obvious. Major media outlets demonized dissent. In a democracy.

Demagoguery is powerfully reduced when it stops getting people elected, and that usually happens because of in-group policing. Similarly, when it isn't profitable for a media outlet to engage in demagoguery, it won't, and that happens when its target market declines to put up with it. Individual demagogues are best stopped by in-group condemnation, and particular strains of demagoguery are generally ended by public shaming.