"MIT's network is a private network and they have complete authority over who gets to access it, in a legal sense and a moral sense"

Then as I said, there are an awful lot of criminals in our society, because people routinely access private networks without permission or in violation of requests to discontinue their access.

"In our society, we do not treat "get off our lawn" and the equivalent as a "polite request." We treat it as an enforceable demand."

Maybe so, but it is also technically trespassing to cross railroad tracks outside of designated grade-level crossings. In my town, there was a brief period where the police attempted to enforce that, and it was found to be absurd and counter-productive to do so: people from every level of society walk across the tracks without hesitation, without thinking about the misdemeanor offense they are committing, and often in plain view of the police. In almost all cases, they are causing no damage to anyone, and so the police do not care -- it benefits nobody to mindlessly arrest everyone who technically violates some law.

"JSTOR at the very least has a moral right to control how he used their private service to download the articles."

Sure, because they own their computers; they are free to restrict access, disconnect from the Internet, or encrypt everything without releasing the keys, and that is fine. They chose not to do so, so why should we care if they do not like the particular program Aaron used, or his particular plans for the documents he downloaded?

"I think most people believe that creators are entitled to control the distribution of their work."

I doubt that; outside of one person who works for the music industry yet to meet anyone who shows even one millisecond of hesitation when it comes to sharing copies of photos, music, movies, written documents, or any other creative work. Most people are perfectly willing to sing "Happy Birthday to You" in public, without spending any mental effort on the idea that it is copyrighted or that the copyright holder forbids public performances.

The only moral issues people have with copyright infringement are when (a) artists are "ripped off" by it (but that is usually something the copyright holders are doing, and is irrelevant to Aaron's case anyway) or (b) when someone claims credit for work they did not do (equally irrelevant here). Copyright as a system has nothing to do with either of these: artists and creative people are routinely "ripped off" without any copyright violation occurring, and copyright does not require attribution (and creative people are often not credited for their work under the copyright system). It has nothing to do with morals, it is a legal framework for promoting businesses that were important to society in the 18th century. It is as morally relevant to most people as a bill meant to promote the laying of fiber optic lines to built Internet infrastructure.

"People think (and I'd argue rightfully so), that downloading a movie should warrant the kind of slap on the wrist"

No they don't; most people think downloading a movie is fine because they want to watch it, and that it is just the fat cats in Hollywood who would care about stopping them. Hollywood has desperately pushed for a moral basis for copyright, but has largely failed: it's too complex and most people cannot be bothered.