Like technical debt, this will come back with full force one day and these corporations will have to deal with the consequences of their lack of forethought.
Nope. We don't have to live with violent insurrections. We don't have to live with sieges of government buildings. All speech is not created equal: there is such a thing as hate speech and speech that inspires violence, and that is distinct from a youtube channel about legos or makeup or video games. They are different things, and people and platforms can decide to say no.
I'm seeing this pattern of hysterical hand-wringing that deplatforming or "canceling" terrorists is somehow a bad thing because it means that—what? now a platform can do what they want with their platform in accordance with their own terms of service? There's this nonsensical and baseless extrapolation that now that platform will just suddenly decide to "censor"—what? who? What exactly are you worried about?
People have been "censoring" and "canceling" each other for as long as there have been human cultures, because there are limits to what a culture will accept, and few cultures are so ideologically pure that they'll accept angry armed mobs storming capitols because "we should debate them". People who are flipping out about YouTube/Twitter/FB/etc limiting the speech of violence-inducing criminals live in a fantasy world where they've never come close to being the target of that speech, and know they never will: they can sit comfortably at home in front of their computers and blithely evangelize about how America is doomed and now America is China and wah wah wah wah because it's trying to do what it's always done, and what it exists for, which is protect its own citzens.
Your concern with violence is fake, as that and the platforms that it lived on, existed way before 6th of January. Parlor was allowed to thrive for years, nobody had problems with it before that. But magically, Amazon is a saint now.
The general problem is that everyone thinks that the ban button and "cancellation" fixes problems. It doesn't. What transpired with these platforms is purely based on political interest and nothing else. This political interest can and will change with next elections and the platforms will follow suit - are you OK with that?
The way i personally see it from afar, no side was innocent and definitely no one scored a win. But social networks messed up the most and will pay the most. Even European leaders expressed more concern with the powers and lack of control over social networks than with a bunch of whatever-you-call-them that took advantage of the laughably weak security force of Capitol (especially considering the event of the day).