Having gone there for undergrad, I do have first hand experience with the culture. I doubt Aaron was as much of an outsider as you seem to think he was. It's a very open and accepting place. Given that his dad worked for them in some capacity, and given that Harvard and MIT students cross register regularly, and where his interests lay, there's a good chance that he was at least socially involved with people there, and that's generally enough to take part.
The social norms there don't resemble those of the country at large or even those of other schools, so I would be very careful about extrapolating what's acceptable elsewhere to what's acceptable at MIT. Nothing about what he did struck me as something that would be very far offbase there, I think it would be seen as a really cool hack. I'm sure the admins would feel a bit different if it caused problems for them, but generally this kind of thing was more than socially acceptable.
To answer your question about torrents, file sharing was very common on the network, but people had much better solutions than torrents (cert. authenticated file servers, internet2, etc).
Edit: Also, c'mon - he wasn't wearing his bike helmet to avoid the cams, he didn't think he was doing anything very wrong. He probably just rode is bike to the building and left it on.