My answer is do what you have to do to win. The whole reason to compete in any sport is to win, there is no doubt that Nascar has rules against rough driving. Apparently Nascar and their officials are not enforcing the rules, why because no drivers are getting hurt and there is no uproar from the drivers, owners and sponsors. They don't really care about the cost of the damage to the cars.
This happens in all the pro sport leauges sometimes they look the other way, however when it comes to a players' safety normally they enforce those rules very strictly. Things like clipping, illegally hitting the quaterback and a pitcher throwing at a batters head in baseball.
In the class I raced, most of the guys owned their cars. The reason you intentionally didn't wreck anyone #1 it was the wrong thing to do and#2 you might wreck yourself and the expense and time to fix your car.
