The incoming VP spent all summer doing exactly that

I haven't used Parler but I'd wager the vast majority of its content isn't. If you want to pick out content, I guarantee I can match post for post with something identical on Twitter.

So why isn't Twitter being targeted?

If the organizing purpose of Parler was incitement and insurrection, sure. But it isn't. And that means they still get 230 protections whether you like it or not.

I think HN is more likely to have overlap with Mastodon and other federated networks. Most of us that seem to be arguing in support of Parler are really just worried about arbitrary and authoritarian approaches to content moderation and infrastructure.

HN is for discussing ideas even when they do not affect us directly.

Disclaimer: I have never used Parler.

But I firmly believe in the principle of free speech and not stifling discourse.

And no, not just over Parler. But maybe over Twitter bannings. And Facebook bannings. And Parler. And deplatforming. Eventually people will build their own internet you can't control, and continue to talk. How will you feel about that? Let's say for sake of argument that that occurs, that a whole segment of society builds their own hardware infrastructure that the tech giants do not control and cannot shut down. What would you want to happen?