Cognitive dissonance is a psychological term. It is to do with avoiding the uncomfortable feeling of holding 2 opposite, conflicting ideas at the same time.
So people make up excuses to ease that tension.
One eg: When i moved to the central coast from Sydney. Bagging Sydney is a loved pastime up there. The area is full of people/families who cant afford to live in Sydney so they have moved up there. But the area is bad, much worse than Sydney and therefore much cheaper.
So instead of people saying "we really love Sydney but cant afford to live there" they say "wouldn't go near the place, what a terrible place to live" even if they really know its not true.
The reality is if they had the money they would be back in a flash.
So in your example you say things to bag expensive German cars or say their drvers are ******s so it makes you feel better about not having one.
Its much better than you saying you love them and want one badly and then denying yourself one.
Its also the reason so many forum members would (and do) say the property market is rising even if we were in the middle of a property bear market. Or a slightly falling market. Or a flat sideways trending market. They don't like the thought of money (equity) disappearing at a rapid rate. You'll see a lot more of it on here in the next year or 3.
Cognitive dissonance is an uncomfortable feeling caused by holding conflicting ideas simultaneously. The theory of cognitive dissonance proposes that people have a motivational drive to reduce dissonance. They do this by changing their attitudes, beliefs, and actions.[2] Dissonance is also reduced by justifying, blaming, and denying. It is one of the most influential and extensively studied theories in social psychology.
from
http://en.wikipedia.org/wiki/Cognitive_dissonance