Time spent in an airplane on a commercial flight is not equal. The takeoff and landing phases are more dangerous than cruising along at 32,000 feet. Driving dangers do depend strongly on time and distance traveled. The premise of the argument is wrong. The idea of commercial flying being safer than driving is not a myth.
That's the lousy thing about no smoking rules on airplanes. When the smoking light went off, you knew you were safe. When it came back on, you knew you were entering the most dangerous part of the trip.