Keys posted active credentials to a forum, and those credentials were used by others to deface a website. Do you regard that as a fair statement of what happened? Still completely insane to send someone to prison for that.
He posted active credentials to the (his words) secret chat room of a "group of renegade criminal" hackers, and pleaded with them to trash Tribune properties --- he was distraught when the people on that channel merely poked around and tried to maintain their access. Ultimately, Keys was disappointed --- again, his words --- with the minimal damage done to his former employer.
It does not seem at all insane to send someone for prison for that.
The actual damages that resulted from his actions were pretty small and purely financial.
Even if you prosecute on the basis of what could have happened (maybe we start charging everyone who runs a red light with manslaughter?), we're still not reaching the level of physical harm to anyone or (barring complete negligence on the part of the Tribune) a catastrophic material loss.
You really think society's need to avenge that wrong is worth spending $30k a year to hold him in federal prison, exposing him to possible violent harm, and depriving him of his future? Sorry, but that's insane. He should pay the actual damages, a punitive fine, and perform community service, tops.