Is there some point in splitting this hair? The salient aspect of this is political speech. Going into the weeds of this “pornography is speech” nonsense is irrelevant to the larger and more essential point that political speech must not be censored by anyone, because it will result in a warping of our system of governance.
I tend to agree that the complete banning of an individual does harm a public forum. But I disagree with you on selective censorship. Those sites will appeal to the courts to protect their ability to uphold their standards and probably win. The sites will argue that law enforcement is too slow and inadequate to stop "true threats" and only they can stop them. That's even fuzzier for incitement where speech is considered to incite the audience to violence. They would claim that right, and the courts would probably back them up.
I think regulation would wind up with a lot of censorship, especially in the form of shadow banning where the controversial content is posted and visible, but doesn't get "recommended" or is otherwise suppressed. The government can't fix that, only competition can. Smashing sites like Facebook into dust for such malfeasance is appealing but difficult to pull off.
Also we still are left with the case of monetized Youtube where poliical speakers expect some income based on numbers of viewers. Aside from the fact that most of the viewership is small (compared to say "stupid cat trick of the day" videos), getting the government involved in payments would be a mess. Thus I would tend to ignore Pamela Geller's complaints about "demonetization".