A significant part of what you're missing is that the function of the actions of the racist manager is to rob the author of political power. Racism works in some pretty subtle subtle ways - by painting the author as 'that aggressive black guy', the manager has already clipped his wings.
You may have also missed this line: After years of arguments with white men (and white women), watching white men (and white women) move away from me when I start to talk about oppression (i.e. what life as a poor black queer is like), I know when to pick and chose my battles
Can you not see just how exhausting it would be to have to constantly explain and justify yourself?