The length of time spent doing something illegal shouldn't absolve guilt that it was illegal in the first place. In my mind it's the same as the mob mentality that overtakes people during riots. Just because everyone else was looting more expensive goods doesn't excuse stealing something cheap.
And he wasn't just sending some traffic to a website. He was participating in a DDoS attack and full well knew what he was doing and what the group was trying to accomplish.
If you're going to break the law to try to accomplish some 'noble'* goal, you have to be prepared for the repercussions of your own actions.
* I'm not saying that his goal was or wasn't noble, but everyone considers their own goals to be noble.