This is basically it; the normal mechanisms don't work properly, and nobody in the mob has any faith that engaging with any formal process is going to achieve a result, so they complain in public.
(This specific incident sounds like a storm in a teacup, but there's far more serious and less visible problems with racial discrimination in academia)
Similar to #metoo. Reporting sexual harassment, assault and even rape quite often isn't taken seriously by either employers or the police. And in the entertainment industry there was a tacit understanding that reporting it would be a career-ending move. So the route that people have started taking is to complain publicly, in an attempt to shield themselves from retaliation and compel the system to address the complaint.
Dr. King put it best: "a riot is the language of the unheard."
Some portion of the mob on Twitter is people chasing clout and performing social justice. For example: I've been attacked for "generalizing nonbinary people" by cis people while describing my own experience as a nonbinary person, so I don't doubt people like that drive a lot of the discussion, but the vast majority is sincere if sometimes misdirected anger at genuine powerlessness. A Twitter riot is much like a physical riot: some agitators, but mostly just angry people denied a voice taking one by force.
The context of this quote is in a speech that is largely anti-riot. It's a warning to the government to not be complacent, but the woke left treats as if he was condoning rioters.
(This specific incident sounds like a storm in a teacup, but there's far more serious and less visible problems with racial discrimination in academia)
Similar to #metoo. Reporting sexual harassment, assault and even rape quite often isn't taken seriously by either employers or the police. And in the entertainment industry there was a tacit understanding that reporting it would be a career-ending move. So the route that people have started taking is to complain publicly, in an attempt to shield themselves from retaliation and compel the system to address the complaint.