This is a general problem, not just for HN. The internet in the aggregate suffers from excessive binary thinking.
Everything has to be black and white, without room for colour or even shades of gray. So discussions tend to create their middle ground not by proportional movements but by jerks to +100 and -100. The more polarized the subject the stronger these reactions will be. Anything involving politics, a brush with the law, religion and so on will create those responses with a high degree of predictability.
Those who feel otherwise do not understand the U.S. Federal legal system. I would like to think Ed understood this when he wrote his original comment; I remember reading his comment at the time, and the only impression I got was that Aaron "dun goofed" and needed to skip to the part where he gets his light sentence. But that was under my assumption that even failing a jury trial with a strict judge couldn't result in more than a couple of years in prison.
I was also surprised that it was the most-upvoted comment of the thread. And it also wasn't the only harsh comment in that thread. So if anyone deserves criticism, it's the Hacker News community for not showing a more compassionate side. I'd rather say it was the responsibility of the community as a whole rather than a single person.
It makes no sense to discuss if anything would be different if the HN community had responded differently to this story, but in general, giving an unsupportive collective response to someone who is down is probably not the best idea.