You're not entirely wrong, but I think the endpoints you're picking obscure the problem. Few people mourn the loss of ethnonationalist discussion, but Facebook's Overton window is going to exclude a lot of mainstream right-wing and centrist thought that goes beyond identity politics. (For example, I wouldn't advise Facebook employees to tell their coworkers about opinions like "welfare programs are bad" or "all responsible people should own a firearm".) That's not just "fodder for the pundits" - it's a real problem if huge swaths of the political spectrum are unwelcome as employees of a major communications platform.