I think the problem for me is the monopoly status this all reveals about the companies involved (Twitter, Amazon, etc.).
If you step back a bit too, there's another issue I have, which is that it seems to me these companies are coming down hard against the idea of free speech. Let's look at it this way: some group believes the Big Social Media Companies are being politically biased in a way they disagree with, in part because of active moderation that reflects decisions by that company about what's "correct" or "incorrect". So they say "hey we're going to start a new social media platform that we don't moderate." This gets used by violent extremists.
Then some other Big Tech companies tell this new company, predicated on unmoderated speech, to moderate their speech too or they will cut resources.
As others have noted, plenty of violent behavior has been organized on Twitter or Facebook, and it hasn't received the same sort of punishment and ostracism. So why Parler? Because some groups on it are supportive of Trump? Because it's the US government? It's hard for me to take appeals to quashing violent behavior seriously when they're so arbitrary in their application at some level.
At some level, it doesn't matter to me, because there's another argument, which is that the platforms should be very removed from the content on them, like a phone company. They could be promoting that, and instead they're going hard in the other direction, which is to support heavy "moderation" by monopolies. I don't want big business "moderating" speech, or having that much power to do so.
My political inclinations are very different from Trump or anything in these insurrections but I don't like the way it's headed, and I don't see the gay wedding cakes as remotely the same.
If there were three wedding cake companies in the entire English-speaking world, and wedding cakes were a universal requirement for getting married, I might feel the same. In fact, in some ways I do feel the same, but I also would say maybe there should be a lot more wedding cake companies.