Like before, Mobboss, you don't know what he's doing with the rest of his money. Even if he wasn't actually offsetting, he might have been donating to green-type projects, charities, and investments. The 2006 hatchetjob didn't explore that, because it wasn't interested.
We can commend that he's spending $400 per month offsetting his CO2, but there's an opportunity cost on that money. It might have a better use, for the actual environment.
I personally know that this is a viable excuse; I don't purchase offsets (I don't even know if they're in my region), but I have put some of my investments towards green companies, hoping to spur their development (through penny share support). If these investments help them (and I believe they do), then I'm already helping do my bit. And, while I'm not purchasing offsets, it's clear that I'm contributing.