Same! For instance, it never occurred to me that Black men have to be especially careful about expressing frustration, because white coworkers find any expression of anger from a Black man threatening. But that's what my neighbor, who also works in tech, told me: that he's basically never allowed to object as forcefully as white coworkers, because otherwise he'll get HR complaints.
There's probably a whole lot of shit like this that we just don't know, as a group, about.
Who would be filing these complaints? Do you think they would primarily be filed by men, women, or an equal mix of both? And do you believe it would exclusively be white people regardless of the gender distribution?
The general thesis of the diversity trainings I've attended is that white men believe they are superior to black men (sometimes consciously, sometimes subconsciously, depending on the fervor of the trainer). White men are racist just by existing - being part of the "white patriarchy" gives them a sense of entitlement and many advantages, whether they are aware or not. So let's say for the sake of argument all that is true...
Then why would a white man ever feel threatened by an angry black man expressing his opinion?
And anyways, what white person in 2020 complains to HR about an angry black man? And if they do, who listens? Get real.
Engaging with this as though it were made in good faith:
A white man might be threatened by a black man expressing their opinion for two reasons. First, the audacity of someone "inferior" daring to express their opinion assertively. That could be seen as threatening. Secondly (and probably more likely) the social conditioning that black people, but especially men, acting with anger are naturally dangerous. That is, someone may feel vastly more physically intimidated by a black man expressing the same opinion, with the same words, at the same volume level than a white woman.
Would a person complain to HR about that? Absolutely. Would HR respond? Depends on the company and the people.
As a personal example, I have immigrated into US from the country with almost no black population, so I'd say that "several centuries of deeply ingrained racism" do not apply to me.
Within the first year of arriving into US, I've had been verbally attacked while I was riding the bus and reading the book. A bunch of teenagers started to say things like "he looks too smart" and "let's take his book away". For a high-schooler who had no exposure to violence before this was pretty scary. Since then, I tried hard to avoid riding the busses through that area. Can you guess which race were those teenagers?
(Note that I have arrived with some pretty weird believes, like the one that everyone with shaved head is a gang member and had to be avoided. That one did not last very long, because there was one person with shaved head in my math class and he was pretty great. Unfortunately, there were no similar experience to persuade me that I should not avoid groups of black people.)
OK but why is it perpetuated today? My contention would be that it is mostly popular entertainment, movies, music, and media that perpetuates this view of the aggressive black male.
I have had little exposure to black people in my life. The few that I have encountered in school or professionally have not demonstrated any aggressive nature. I have no first-hand experience of aggression by any black man. My parents did not teach me that black men are aggressive. I did not learn this in school or from my friends. The only way I can think of that I might have gotten this impression is from movies, television, music, and media. These are the same people who are now professing and demonstrating how woke and concerned they are, rather than apologizing for their roles as the primary perpetuators of a stereotype.
Therefore when I see media or entertainment figures (I include politicians here) on the anti-racist soapbox, it all falls rather flat for me. They are the ones fanning the flames on one side, and demanding attonement from everybody else on the other side.
There's probably a whole lot of shit like this that we just don't know, as a group, about.