There are legitimate business concerns:
1. What if it turns out that Facebook Groups were utilized in the effort by some in the mob to capture members of Congress in the Capitol and hang the Vice President, and that some of this was explicit ahead of time? This isn't theoretical -- keep in mind that the group planning to kidnap Gov. Whitmer organized on Facebook. Did Facebook play a role in promoting people to join that group? This creates not just PR problems, but also hiring problems. Who wants to write the algorithm that recommended a hate group and play a role in radicalizing people to violence?
2. A key moment from the Congressional hearings into tech companies was when Jack Dorsey, asked if the cure for bad speech is more speech, replied: "All of our policies are focused on encouraging more speech. What we saw and what the market told us was that people would not put up with abuse, harassment, and misleading information that would cause offline harm, and they would leave our service because of it." It's hard to fault these companies for wanting growth, and kicking people out can actually encourage that growth!
3. Young people are often the most profitable audiences. And many of the key creators for those audiences are also young. It's a serious problem for YouTube if their brand becomes Rudy Giuliani instead of [whatever makeup vlogger is popular right now]. This is similar to point (2), but slightly different. Even a smaller audience can be more profitable.
To the "no alternative" point, I'm sympathetic to anti-monopoly efforts. Mostly for my own left-wing reasons: https://democracyjournal.org/arguments/imagining-a-democrati...
But also, these efforts should be broader than just the technology companies: http://concentrationcrisis.openmarketsinstitute.org
That said, even if you took these actions, it'd be hard for any company that wasn't taking moderation seriously among people planning violent overthrows of government. (Which I think is a good thing. Companies should care if armed insurrections are openly being plotted on the merits, not just for business reasons.)