"White Fragility" describes a phenomenon of defensiveness when confronted with having to self-reflect and/or consider one's complicity in a greater structure of systemic racism and points out that is a symptom of the fact racism is not a function of "a few evil people" but is in fact a social system that requires buy in by both the ruling class and the greater part of society. That's all.
This might seem a 'no duh' concept, but the fact that people like Robin DiAngelo and Jane Elliot receive such severe pushback in their professional fields (Human Resources and education, respectively) for verbalising it and formulating their lesson/work plans with it as a basic assumption underlines how racism has insinuated itself in the cultural narrative to the point where it triggers such visceral, emotional reactions. Much in the same way that terms like "cultural appropriation" or "toxic masculinity" are by themselves neutral, but because they needle at certain cultural pillars it produces reactions like...Well, there's an entire genre of videos on the internet devoting to ranting angrily about Greta SarkeesiAngelo or whoever the fuck TheDonald and CTH's lurkers decide to hate on this week.
And as Endus pointed out, the behavior is similar to climate change denialists in that the bar for action or resolution is deliberately set at a nonsense level because the point is not actually to discuss the problem, it's to shut said discussion down. Much in the same way people bitching about White Fragility aren't actually interested in whether or not the concept exists and how that ties into the failure of previous reform efforts like Reconstruction - i.e. something you should ostensibly be interested in figuring out if you actually give a shit about something besides stirring the pot - they want to stop the discussion entirely. Hence the presence of bullshit arguments like "people could make money off this ergo it's not true", or "well so what, identifying it hasn't solved racism so I guess you're actually the racist".