This is the classical fallacy of division (See, for example, http://www.nizkor.org/features/fallacies/division.html). Note that it is *possible* that an *individual* smoker might be immune to the harmful effects of smoking, but this is clearly not a feature of the group of all smokers. Therefore, your claim that this is a logical argument is the actual problem.

Now, if none of your readers identified this correctly, I would argue that your experiment failed. I require my students to be able to identify such mistakes in news articles they read for class.