It may have been premature for Amazon to remotely delete under 17 USC 503 and 509 but those sections clearly authorize a court of competent jurisdiction to "order the destruction or other reasonable disposition of all copies or phonorecords found to have been made or used in violation of the copyright owner's exclusive rights, and of all plates, molds, matrices, masters, tapes, film negatives, or other articles by means of which such copies or phonorecords may be reproduced." Amazon, having the technical capability, might have been compelled by order to exercise that capability. Now, Amazon did not have to resort to deletion without a court order but may have seen the writing on the wall: either get screwed by the publisher for willful copyright infringement or screwed by a class action breach of contract by Kindle users and picked the lesser of two evils.
Ideally Amazon should have bit the bullet for the consumer experience by docking the company who put the unauthorized 1984 up on the Kindle marketplace and getting authorization for either the existing or a new copy of 1984 for its consumers in as seamless a transition as possible but of course then the shareholders would have gotten angry and sued Amazon for doing something clearly unprofitable leaving pretty much no one happy.