The way I read it at least, it was in a place where a non-smoking policy was in effect, and probably the author had previously asked someone not to smoke, and gotten the response "oh, you can't really be allergic to it."
If that's true, then someone trying to hit him would probably be about on par with most of the responses I get when I point out to people that they're smoking in a non-smoking area. Apathy and aggression are by far the most common responses, which is why I usually just complain directly to whatever authority happens to be present and make them deal with the problem. Unfortunately that doesn't work either...I can remember going to the security guards to complain about people smoking in the airport outside of the designated smoking area. I found the guards patrolling with lit cigarettes.