At the end of the day, when people have spent many thousands of pounds / dollars / etc on a car, they've made a huge investment in it - both in terms of money and also emotionally. So it's natural to defend that choice.

If people with hybrids were to try out the modern diesels, I think they'd be impressed, and vice versa also - if the people in the TDIClub were to drive a hybrid for a year they'd also like them. While I have a TDi, I read the hybrid forums (here and cleanmpg) instead of the TDi forums since I think I can learn more from understanding a different type of car.