I would guess that the answer is that not all anti-racists know all the code-words. Thug, urban, inner-city and so on are all known because they're the most used.

To contrast, I used to have a couple of friends who would use the term "friend" as a stand in for n* when talking about people in public. I figured it out from being around them and hearing how they stressed it differently than normal, but any random stranger wouldn't have picked up on it.