Here's a blog post and comments that contain many of the thoughts, right or wrong, surrounding the anti-diesel movement. As you may have gathered from my previous posts, I think it is dumb to ban diesel cars in America (which is essentially what California has done, aided and abetted by Massachusetts, Vermont, New York, and Maine).
Until the infrastructure is in place to transport all goods and persons using electricity (which implies a massive shift to rail, of which I am a keen advocate) we need to be clear on the advantages that diesel offers over gasoline in internal combustion engines. With diesel you get more work per unit of fuel and per unit of pollution.
Any meaningful discussion of vehicle efficiency and pollution must take into effect the amount of work being done by the vehicle. Carrying one person to work and back once per day is way different from hauling one contractor and his tools from job site to job site throughout the day. That's how a lot of gasoline is consumed and there are no easy answers on the market right now for contractor who wants to go green while still hauling hefty loads.
So I'm getting tired tendency to focus on passenger cars as the root of all pollution and fossil fuel dependency. Drive past any diner at lunch time and you are likely to see a raft of pickup trucks that are being used for work, not just going to work or the grocery store. If they were diesels they could still do all that while causing less pollution.