The judge disagrees with you. Since he could have been imprisoned for up to ten years, he got off comparatively light. Especially since the sentencing recommendation was 7 years. Keys’ attorneys argued that the actual damages to Tribune company were (as you imply) very light and did not pass the $5000 threshold for imprisonment. The jury disagreed. The judge can’t change that.
Yes, changing laws is hard. But Congress critters respond to organized constituent pressure. If you don’t want to take up that challenge, then you obviously don’t feel that strongly about the issue.
You can certainly think that it is disproportionate. I do too. But you can’t argue it was invalid. It is in line with existing law. And since Keys provided his credentials to Anonymous and encouraged them to “go fuck some shit up,” I have a hard time working up sympathy for him.