Given that a smoker can't smell it themselves I would suggest that "rude" is a bit over the top...
Yes.. it is unpleasant.. but no more unpleasant than many other smells people bring with them... from food, or lack of personal hygiene or excessive perfuming.
Why pick just smokers? If they do not attempt to smoke ON the aircraft they are going nothing wrong. Smoking is not (yet) illegal.
The usual sarcasm is clearly invited here... If you cannot cope with entirely normal interactions with other people... fly on a private jet.