Slur or not, being characterized as racist can cost someone their job, their home, their social standing. Calling someone racist isn't to be taken lightly. It's more than just a teaching moment. Even racists don't call themselves "racist" anymore. They're "race realists".
Nor are these race realists looking to build their white ethnostate to avoid feelings of guilt. Most believe that liberals seek a "great replacement" of whites, & they wish, for whatever reason, to preserve whiteness, untainted. Many also believe that people of color are drawn inexorably toward criminal & other anti-social behavior.