I was the same, I like to think, when I did smoke. I gave up in 1993. I always tried to keep away from anyone whom it might offend and was very mindful of it doing so.
As an ex-smoker, I'm now so anti-smoking that I find it intolerable to be anywhere near smoking. I guess it's only through quitting that one can fully realize just how dreadful it is to be in the company of smoking.
As for anyone with a chronic and/or acute respiratory issue, of which CF certainly is, it's an absolute no-no for them to be anywhere near to anyone smoking or smoke of any kind. Some people will just never get it and, even if they did, would be far too ignorant/arrogant to be mindful of it anyway.
If you think you may have over-reacted, you should see me!!
cheers and best regards
Lindsay