It sounds like LeCun stepped away from twitter and that thread because he was fed up with the toxic discourse and did not attribute that to Timnit in particular. Its strange that OP post sounds exactly like what LeCun was asking people to stop doing:

".. I'd like to ask everyone to please stop attacking each other via Twitter or other means. In particular, I'd like everyone to please stop attacking @timnitGebru and everyone who has been critical of my posts. Conflicts, verbal or otherwise, are hurtful and counter-productive... " -- https://twitter.com/ylecun/status/1277372578231996424?s=20

TLDR : Yann Lecun tweeted that ML models are biased when the dataset they are trained on is biased. Bunch of people, including Timnit Gebru, replied he is wrong and the biases are every where and systemic.

Yann later tweeted again to explain what he meant in the context of deep learning models without hand engineered features, but people ignored him and still replied he was wrong.

It looks like they were accusing Yann of all the systemic biases of society... common.

Is there a paper showing that the Transformers based models are "biased" no matter the dataset ?

This episode happened during the blood moon of Jacobin Twitter this summer. I saw colleagues denouncing colleagues for “liking” the wrong tweet.