The definition of "computer trespass" isn't unreasonable. It should be illegal to break into a site and deface it, just as it should be illegal to walk into someone's house and put up a poster. People need to respect boundaries.
What's insane is that there's no gradations based on the seriousness of the conduct. Any crime punishable by a year or more in prison is a felony, and "computer trespass" is punishable by up to 15, even if the sentence is ultimately a slap on the wrist. In contrast, the meat-space equivalent of criminal trespass is a misdemeanor as long as any property damage is under $500: http://law.onecle.com/georgia/16/16-7-21.html. For more serious property damage, there is a separate statute, with different degrees of severity.