No one is defending calls for violent overthrow, but typically we hold the people that have actually committed the acts responsible. Here, we're shifting the responsibility a level above with the sentiment that "this happened on your platform, so you have a duty to moderate". The kicker is that these tech giants employed the polar opposite of this philosophy for the majority of their existence to eschew as much responsibility as possible for their users' content.
Let's see. If I go and organize a violent insurrection using GMail, what does Google need to do to comply with it's own philosophy here? It seems that it needs to start scanning all emails for inciting violence and send them to a moderation queue. Of course, it's never going to do any of that, because unlike Parler it doesn't have any overlords holding it by the neck.
Google, Apple, and Amazon like to do whatever they can get away with when it comes to anti-competitive practices, and enjoy the protections granted to them as private entities. On the other hand, this shows that they're willing to also take unilateral action to silence millions of people, based on nothing more than a whim and a holier-than-thou attitude. There's a messy contradiction here. They're not subject to having to abide by the 1st amendment because they're private companies, but in practice they're in control of the majority of public discourse. This is a big problem.
And this returns me to what I think was a big point in the article. The response to any free-speech concerns has been: "if you don't like Facebook or Google's policies, you're free to create your own." But the sway of FB/Google's policies is no longer just over their own content, but also the platforms they manage. Which as it turns out, form the majority of the infrastructure of the internet.