I'm a Matt Kenseth fan that was hoping for Greg Biffle to win the race (see my Fantasy NASCAR picks).
At this exact moment in time**, the flag man has probably just realized that there is a potential problem. However, race control in the press box is responsible for calling for the caution, not this guy. If that one car spins to the bottom, and no debris is left on the track, they probably let them race back to the line.
However, by the time the dust (and debris) settles, the cars are already over in turn 1, and there still definitely needs to be a caution. I liked NASCAR's decision to let them race as far as it was safe to do so, and then slow them down before the debris posed any hazard to the drivers.
Clint Bowyer said after the race that it was the right call, and I agree with him.
**At the speeds the lead cars are travelling at that time, they will pass the start/finish line long before the flag man can potentially reach for and raise a yellow flag to display it. He had absolutely no chance to beat the leader with the yellow flag, even if it was his call to make.