Diesel isn't dirty, it's just another hydrocarbon fuel. The engines can be as clean or dirty as you want them to be. Just like petrols.
All the buses I rode in when I was in California 10 years ago were diesel. Natural gas engines are a lot less efficient and have issues with range and refuelling.
The American public hates diesels because in the 70's the US auto makers made the worlds worst diesel engines. The public still remember that. They are completely unaware that the quiet and smoke free car sitting in front of them at the lights is actually a turbo diesel.
All they remember from the drive home was that retard in the flat billed hat who screwed with his diesel pickup so it would "roll coal" at every intersection.
France's situation is ridiculous because future emissions rules are going to have parity between petrol and diesel. Further, if everyone drove newer, or even in tune, vehicles the pollution problem would solve itself.
So targetting diesel vehicles is pointless. They should instead be targetting polluting vehicles of any type.

