[gfodor]

The argument is Facebook and Twitter are doing a better job of moderating, and Parler isn't or is outright not moderating their content.

This may well be true. But the point is now we're arguing a very subjective standard, and the determiners of those standards aren't a judge or jury, but a few CEOs. The standard of "when is it justified to refuse to host an entire platform based upon the nature of how they moderate their worst content" is an incredibly complex question, with no objective answer, and how these company's answer it has a profound effect on freedom of speech, since deplatforming a site like Parler doesn't just censor the speech of those who ought to be censored (by any standard), but everyone else on the platform.

It's fairly obvious where this will lead, but I doubt we will correct it before it causes immense harm (not necessarily directly, but due to the blowback that will come from censorship without due process and tit-for-tat escalation.)