If society fails (which is little more than a prepper wet dream) everyone's going to go gunning for whoever has food and fuel. No one will care about Google or political parties.
Before civil rights, "private businesses" used the same exact excuse as big tech while refusing customers based on race.
In the current setup, big tech thrives risk-free via governmental protections separating them from their customers (or what their customers post on the platform). The underlying concept of social media has become a public utility, and should be protected as such. Once big tech began altering visibility of posts based on politics (in any way/shape/form), they crossed the Rubicon.