Why even discuss this? How can you expect good intentions from your white coworkers if these are the types of discussions going on publically in the company?

Race agnostically, it is an obvious statement and should be part of company guidelines : "bigotry will get you fired". Simple.

Similarly, how can anyone believe that saying something like "violent black men should be fired" is okay? Just address violence in the workplace race agnostically in your company guidelines and don't tolerate it.

Is this really complicated?