Modern diesels, sure. Latest offerings from BMW, Mercedes or Audi are actually super clean, especially if equipped with an AdBlue system. But get out on the road and you see people still driving 90s diesels which emit huge plumes of black smoke every time they accelerate, and I know people who buy brand new cars and the first thing they do is cut out the DPF, EGR and pretty much every other emissions reducing system "to keep the running costs low". It's a disgrace, and older diesels should absolutely be straight up banned in cities with very harsh penalties for modifying modern ones(in UK removing the DPF attracts a £5000 fine, but in many EU countries it's still not a problem).