I'm not going to bother hiding the spoilers for Sorry to Bother You because I don't think they're worthwhile... The first half is fairly tame and routine critique of dead-end jobs and the day to day grind that tends to accompany it, and how union organizing is supposedly our way out. But because of the alternate reality, the sharpness is dialed up a few notches with the inclusion of companies like "WorryFree" who promise steady housing and food (looking exactly like jail cells but with bright colors) in exchange for literally lifetime indentured servitude...
Thus far, this is a fairly rote Marxist critique of capitalism. The workers are exploited to enrich the capitalists, and petty bourgeoisie like Cassius are recruited into the ranks of enablers tasked with sustaining the systematic oppression. I'm guessing that perhaps Boots Riley realized he needed more of a "hook" to draw people in, because I have no other basis to explain what happens next.
Enter the half-horse half-man people. Completely with gigantic CGI cocks.
Within the universe, WorryFree secretly dovetails into genetic engineering to make their slave labor more efficient overall. So the "Equisapiens" are heralded as stronger, more versatile, and with far more stamina. So capitalism is bad because...horse people? I don't know. I'm definitely not the only person confused by what exactly Boots Riley was trying to say with this plot device.
I thought Sorry to Bother You was pretty good as a piece of satire, even though I am much more pro-capitalism (or, to be more precise, pro-free markets) than the director of that movie.
The intent of the horse people plot point was pretty clear to me: it's a literalized metaphor for corporations dehumanizing people. The protagonist, up to this point, had been making successively more egregious moral compromises in pursuit of climbing the corporate ladder. Each compromise was accepted by uncritically embracing corpspeak justifications and succumbing to social pressure from colleagues and bosses who appeared to sincerely believe those justifications. The absurdity of these compromises is partly played for laughs, but it's also a challenge to the audience to think about whether they make similar moral compromises to please their boss or their coworkers.
The horse people represent the point where it boils over for the protagonist, where a line is crossed that he can't condone. Its absurdity is the point: the evil corporation he works for has led him to embrace complicity in moral compromises that far surpass what the audience would like to think they would accept. The movie, having made the protagonist complicit further, offers something truly, deliberately absurd to start the character and plot transition from the protagonist being complicit in the system to actively fighting against the system.
The movie has the protagonist draw the line after something unthinkably absurd, and challenges the audience to ask themselves where you would draw the line and where you should draw the line. But it does more than that: it suggests that society draws the line even further: when the protagonist tries to tell the world what is happening, the evil corporation's stock value soars and politicians congratulate it for its innovation. Is this realistic? Probably not, but it is meant to appeal to a sense that society's moral compass is slower than your own, a sense that everyone knows that something about the system can be fundamentally broken and yet the elite seem to revel in this brokenness.
This is what satire is supposed to do: amplify the absurdities of the familiar and use the shock and cognitive dissonance of the extreme result to critique those more mundane absurdities in our life. We don't literally live in Orwell's 1984, but we feel the parallels from the novel to a sense of oppressive inability to speak the truth, a wariness of government surveillance, a gnawing distrust that your neighbors will side with you over the state, and a bitter cynicism that the public credulously believes whatever the media tells it. Sorry to Bother You is satire for the moral compromises we make at our jobs, starting with the simple faux-civility of a salesman pushing a product on someone who doesn't need it.