Yes LeCun is right to focus on his tasks as a researcher in research labs, papers, conferences. However, he is also a leader of the field when speaking to the outside world, which is what happens on Twitter in heated arguments.

I think he has some responsibility to at least acknowledge the complexity of this issue in such cases. Not speaking to the public is also a option if he doesn't like the leader role, so him deleting twitter is a completely ok thing in my eyes.