He didn't do "a bit of scraping", he tried to download the entire archive. On a guest account at a university he had no relationship with. Over a period of months. He was blocked with increasingly wide-reaching measures and reacted with increasingly elaborate circumvention attempts, culminating with a laptop hidden in a closet.
His intent was very clearly criminal.
No, it's not. But doing it to get around people blocking your computer is. Likewise firing a gun isn't illegal, but attempting to hit someone when you fire a gun is illegal even if you miss. Intent figures into guilt and inncense in most matters of criminal law.
Swartz clearly knew that his IP address and then MAC address were being blocked specifically. You could argue he might have thought that it was just traffic shaping, but that wouldn't explain the MAC block.
EDIT: Clarified by adding 'criminal' in front of law.