Well, originally we were discussing whether a premium German diesel sedan from Munich is a sporty vehicle. And no one can be after a diesel sports car purely because there is not a diesel sports car on the market. Thankfully. I don't want a 911 Diesel S. Eh.
And bringing Le Mans to this is a bit off since it's another league, something different. Audi is using e-tron's to show what they can do and what is possible within the regualations and within the limits of today's technology. It's basically the same scheme as the so-called hypercars - P1, LaF, 918. Porsche used the hybrid technology, again, to show what is possible. They could have built the 918 without the e-motors , batteries and such. And make it lighter and faster than the Carrera GT was.
/endofftopic
Diesels are just a rational choice. People are buying them because low MPG, yo. You know, for someone, who does 200 km a day, are ~ 3 liters in favor of diesel a lot. Another reason, as I see it, are (were) the old lazy NA petrol engines choken up by emission regulations. Turbochargers really helped them petrols, latest variation of VAG's 1.4 T(F)SI is really good, fast and yet has great MPG for example. So you really have to do your maths to find out if a petrol or diesel is the right choice... Unfortunately, some people don't look left and right and go straight ahead for diesel blinded by MPG in brochures.