It is easy, you tell anonymous kids behind a keyboard "People will get unhinged if you use XXXXX words" or say "XXXX things" and they do it.
Most of the time it is because it makes otherwise sane adults completely childlike and overly emotional in their response. Said 'adults' tend to go overboard in their response to these racist things because it brands them as 'the good guy' and makes them feel good about themselves thinking they are a champion for a cause.
I'm all for getting people who use these terms repeatedly banned or perma-muted, but please for the love of god try and be mature in response when you encounter it. 95% of the time it is some kid or 'adult' trying to get a rise out of people.