No I wouldn't buy a diesel car under normal circumstances. They are too polluting and people are beginning to realise this.
I wouldn't buy a hybrid or electric car either. These are a technological dead end, buyers think they they are being green but they are not. Lower emissions from your car, but you are just transferring the problem. How does a landfill site filled up with dead, unrecyclable batteries help the environment? How does coal-fired electricity help the environment? How does buying a car that is more damaging to the environment during its construction than a traditional car help?
I am open to hybrid/electric power in the future, but until someone invents a fast-charging, slow-discharging and above all recyclable or biodegradable battery, it is delusional to believe these are good for the environment or are somehow "the future". Car manufacturers are brilliant at marketing these cars to a certain demographic, that smug demographic who doesn't want to reduce their car usage but wants to be seen to be "green". But being smug, being seen to be green, is not the same as being green.
An efficient petrol engine that is well maintained and driven well is the best option available at the moment, environmentally-speaking. If you want to reduce emissions, don't over-rev, don't stamp on the brakes, and above all, use public transport where it is available.
Of course, using the car less is not the choice for most people who like to pretend to be concerned about the environment. They worry about too many people driving and making unnecessary journeys, yes, but that doesn't mean them.