>>dang+(OP)
If you're dropped into a totally foreign culture and one remark to your guide results in a slightly-discomfited "that's not really how we do things" then you might not think too much of it, but if you venture a comment that's met with an expression of abject revulsion, you know you've said something unacceptable. We're all constantly calibrating our sense of such things in everyday social interactions and those normative pressures ultimately define acceptable discourse. At the moment the Overton window unfortunately admits some very ugly things and I'm not sure it makes sense anymore to persist with gentle nudges in the right direction given the manifest urgency of the problem.
Those unwritten rules that govern social behavior can induce real internal change too. People's attitudes and beliefs are shaped by what they perceive to be customary and deviant in their culture.