I kinda like the clackety sound of a fully-mufflered Diesel engine. Very nostalgic.
Diesel engines have a potential to be clean. The fact that VW, et al. can pass the emissions tests proves that they can clean up the emissions, if they wanted to. They just got too greedy with it. They wanted to push the performance and fuel economy to the envelope... in other words, they wanted to have the cake and eat it too.