But I don't see how how you can consider it a "fallacy". Where is the flaw in the logic of "I want my family safe. In a collision, the occupants of the larger vehicle are safer. I will buy a large vehicle."

Of course the occupants of a smaller car are more at risk. That is the point. They don't want their family at risk. They buy the larger vehicle. I doubt the possibility of smashing into a smaller car enters into the decision. I would guess they think something along the lines of-- I would never plow into anyone else. But if they hit me, I want the most steel between us I can get.

Unreasonable, maybe. Thoughtless, ditto. Understandable, absolutly.