I agree with your moral analysis here, and that the prohibited thing should be the distribution of protected IP, not simply retaining a copy of something you already had rights to view (which I think there is substantial precedent for).

This is the big problem with the DMCA. It shortcuts the messy dirty work of dealing with IP violations, to the benefit of large corporations and the detriment of individuals. The former engage in rampant abuse of their powers under the DMCA, apparently without any fear of significant consequences. It's just another example of the degree to which large corporations own America.