Yes but BMW and Porsche were just not German, they were active military equipment manufacturers. BMW for plane engines I believe and Porsche manufactured vehicles and tank turrets.
That's not the point. The point is that it wouldn't make sense to hold modern German companies responsible for acts in WWII if, nowadays, the German government and German populace honestly and openly condemns the actions of the Third Reich and its supporters. In fact, the modern German populace and government DO condemn Nazi Germany--quite vigorously, in fact.
The people running BMW/VW/etc nowadays had nothing to do with whether or not those companies assisted the Third Reich. By boycotting BMW, I'd only be punishing people who condemn the Holocaust and had no part in causing it. That just doesn't make sense to me.