Love it when all the 'anti smoking' lobby come out without actually answering the question,
My last airline that I worked for flew into Afganistan, at the height of the troubles, to bring some British troops out, 3 rotations as I recall at approx 300 troops per time. The airline was non smoking but the senior hostie, who also happened to be the cabin services manager, had a word with the commanding officer and a 'free for all' ensued, 'smoke as much as you like boys', they'd been under such pressures for a number of months so why prolong their agony, ''if you want a fag then have it''
This business about causing damage to aircraft is nonsense, it's all about what is morally right, did aircraft crash for the 50 ish years that, and due to, smoking was allowed?
There can be exceptions to the rule if we, you, didn't live in such a black and white world.