LeCun focused on the narrow technical question of statistical bias. Gebru and many many others have raised the point that an algorithm which works equally well for all skin tones will still have a societal impact, and they want to question that impact. How does a given new technology shift power? In whose favor, and at whose expense? That's the question which is arguably more important than some accuracy on a benchmark -- which as LeCun points out is easily solved with a more representative dataset.
Have you engaged with any of the critical study of AI, from Gebru or others, like the AI Now Institute at NYU or Ruha Benjamin at Princeton, or one of the lots of other scholars even in that one Twitter thread? The results of their work have included the recent IBM and Amazon moratoria on the sale of computer vision technology, and likely others to come.
The fact that LeCun refused to engage with a valid and deep criticism of a paper (which was not even his), to me at least, indicates a lack of willingness to engage critically with the social impacts of computer vision. Gebru's tweet pointed out that lack of willingness and her frustration with it, and also the fact that LeCun has had ample time to hear of it (it is in the news a lot, especially after these Amazon and IBM announcements, but groups like AI Now have been describing this for years.)
How about some empathy for Gebru? I would argue that she actually has more on the line than the single most celebrated individual in computer vision in this situation.