On the matter of Parker, Apple likely banned Parler because of exposure to criminal, civil, and PR liability. Per the CEO of Parler, banks and payment vendors, law firms, and text and mail services also cancelled on them. That’s why people are talking about alternative currencies in the same breath as Parler.

Anyone too slow to ban Parker could face a full court press from all sides, and not merely any one firm. Apple has also banned porn and that is not legally required at all, and somewhat ideological.