The name Diesel comes from the surname of a German engineer, also famous by his strange death and at the same time prone to conspiracy theories. What's true, however, is the efficiency of the engine but at the price of higher pollution, especially in PM2.5, PM10 and nitrous oxides or dioxides.
Clear enemies of the clean air, these motors are much more perceivable by the senses as they emit more particles and a characteristic heat, sometimes even a dark smoke. Sadly multiple people only see their wallet, without worrying about other factors. Not an advisable policy as the air remains public and everyone experiences health problems with the pollution, so higher means more probabilities of problems for everyone in a close proximity.
The industry should rely on regulations, engineering solutions, and not lying to the world as it was discovered in a recent scandal. Governments shouldn't allow these motors like they are today, as neither two stroke engines or combustion engines without catalyst or other methods to filter the exhaust gases and particles.
Not for being alarmist, but to be in a severe pollution scenario could be compared (or even worse) with smoking, and today almost no one doubts the risks of smoking. Allergies, and respiratory diseases aren't as well nice for a nice experience of life.
There's time to think about the reality of public transportation, or how is not necessary to use a vehicle in short distances. Bicycles are pretty fast. Sharing a vehicle between several people, or buying the cleanest one. One must be worried about the air that breathes, right?