Re removing stuff already sold: no-one can pass on a better right to goods than they themselves hold. If Amazon are in breach of copyright in making the sale then you have no right to continue to hold the electronic goods sold. No more than you can keep stolen goods such as a bike, even if innocently purchased.

Nemo dat quod non habet, as the legal eagles will say.

Of course if such a sale took place and Amazon refused to refund the money when deletion happened a case for action would arise.

I also quite agree there is something sinister about the ability to amend or erase the goods post-sale. It might tempt some to immediately back up any possibly controversial works on a separate device inaccessible to Amazon. I don't know if the devices are set up to allow such backups, but I'll bet some hacker can make it possible if it hasn't been done already.