Your argument discounts the existence of segments of society who have fantasies about race and class war or the overthrow of the government or that they're being oppressed. c.f. things like the militia movement, white supremacists, Neo-Nazis, and Dylan Roof.
There are a lot of people to whom Hatred would genuinely appeal: the target market is in the name. Can they sell 40k copies worldwide? If Resistance Records could in its heyday, sure. It's a lot easier to get your hands on a Steam game too.
In Hatred you murder people of every race, religion, class, and gender, I don't think that would appeal to the people you describe. not without any mods anyway, of which I am unaware of any existing. The segment to which Hatred would legitimately appeal would be edgelord teenagers going through their misanthropic phase. but even assuming you were right on who it appealed to, are these people who would be technically savvy enough to own a computer powerful enough to run the game? or even to know of steam? would they be gamers by any meaning of the word? Ignoring even those barriers to entry, are there even 40,000 people of the class you describe in the country? (honestly asking, I don't know how many of each of those groups there are)
I honestly doubt more than 5% (being really generous here) of the people who bought that game did so because they enjoy the narrative unironically.
[edit] googling "Resistance Records" lead me to
this which I think would be more in line with what you are thinking and it doesn't look like it sold better than a few thousand copies ever. [/edit]