There used to be a certain degree of courtesy and understanding among drivers. If a car was holding you up, you would give that car a little bump to let the other driver know that you were there, you were faster, and you were going to pass. If the slower driver did not voluntarily move over, you pushed him up the track and completed your pass. I'm guessing what really happened at Martinsville was that Chase was eager to get that first win, but wasn't quite as fast as Denny on the first few laps after a restart. Denny was faster, Chase was not willing to give up the lead, Denny applied the front bumper of his car to Chase's rear bumper, but did it so hard that it actually lifted the back of Chase's car and doing that in a turn is guaranteed to spin a car. The outcome might have been very different if Denny had applied that pressure upon exiting the turn. Both Denny and Chase had Homestead in their sites and a win would get them there. The stakes for these drivers are very high and that can lead to some poor decision making. It makes it exciting for the fans and that is what NASCAR wants.