In my long decades of experience looking at used cars to buy for myself and as a friend to others, having looked at well over a hundred cars, and also my experiences as a young man working at a rental outfit, wherein I observed the conditions of cars returned I found a sure and strong correlation smokers and abuse of car.
That’s what I thought. If you would have said you were basing your observation on just your own experience (maybe extensive: You sound like a used-car salesman), this trip would not have been necessary. Now we can all discount it as rubbish.
I can just as easily have made the opposite claim by making an observation that most of the mechanics I have known over the years were smokers (a much larger share than the general population). It can be assumed auto mechanics are likely to take better than average care of their vehicles, therefore you are refuted unless you can link some sort of scientific study to prove your original argument that smokers take poor care of their cars.
But you can’t, which is MY original point. I chose not to make that argument because it is unnecessary...you failed to prove your argument.