If you have a sufficiently persistent person and inflexible moderation policy, one person really is enough to destroy a website.

I agree that destructive people can do a lot of damage, and that removing them is a good idea. I also agree that destructiveness doesn't even require maliciousness.

The strategy I'd like to see is "cultivate dissent." If someone is being critical in an unproductive way, then show them the productive way to be critical, and if they fail to shape up, then remove them from the community, through a ban or deletion/hiding of comments. Documenting the steps along the way, and linking to previous warnings, makes it clear to observers that dissent is carefully managed, not suppressed.

Tying the moderator reaction to whether or not the criticism is fun to receive, rather than if it is useful to receive, is a recipe for receiving fun but useless criticisms and not receiving unfun but useful criticisms.

Receiving and processing unfun but useful criticisms is a core part of rationality, to the point that there are litanies about it.