For economy to work, large number of people who dislike each other need to cooperate, so it is generally a good strategy for the society to arrange consequences in such a way as to not cause escalating chain of feud.
If there’s a bar where the owner lets a gang hang out and recruit members and plans crimes, the thing to do is shut down that bar. Not let it go unchecked because the gang will be mad about it.
That said, Parler is not being shut down.
Also, Section 230 has nothing to do with AWS’s relationship with Parler.
Then the thing to do is call the police, not gather a mob to shut down the bar.
If people openly plan violence on Parler, then shutting it down will only make it harder for police to prevent it.
Parler’s business partners are abandoning it, sure, but that’s by no means a “mob”. It’s much more akin to the bar’s suppliers refusing to sell it ingredients for drinks, if we want to stick with this analogy.
AWS, Apple and Google deciding on behalf of 3 billion people what they're allowed to read, most certainly does.