I can't justify this, but I can't help thinking it. At least I know it's not fair.
Sometimes, my lizard-brain is doing its thing turning my head towards attractive representatives of the fair gender, simply because looking at them is enjoyable to the lizard-brain (and to the higher layers of brain, too, in various ways). Some women are more attractive (here I mean strictly in terms of appearance) than others, of course. But if you take the most attractive possible person, someone who approaches whatever ideal my lizard-brain leans towards, and then you put a cigarette in her hand, all that attractiveness vanishes instantly and irrevocably.
It makes no sense, really. I'm only looking at her as I drive by because looking at her is a pleasure in and of itself. It's not like I'm going to ever meet her. It's not like the cigarette actually changes any of the things I was appreciating a moment before. If I happened to see her a minute earlier, before she lit up, I might have gone by, appreciating her form, and that would be that. But the idea of her smoking is so thorough a turn-off for me it erases even that completely casual appreciation.
The same would happen if it was more than a casual glance on the street. If I met someone and found her attractive in more ways than just appearance, if I found her mind exciting, her attitudes complementary to mine, found everything about her interesting, still the idea of her smoking would completely shut all of it down.
The idea that she's an ex-smoker wouldn't bother me too much. Maybe a little twinge, but I'd get over that no problem. But a current smoker, even one who intends to quit, who is in the process of quitting... I could be friendly, I could be supportive, I could be a great guy, I could even conclude in a dry rational way that I would find her attractive after she quits, but I can't find her attractive.
(All the female pronouns would apply equally to males, though I started with talking about females simply because the lizard-brain-appreciating-eye-candy thing only happens for females for me, and that's how the post started.)
There's nothing wrong with being turned off by the idea of smoking, but it doesn't make much sense for it to be such a complete veto of everything else, no matter how it goes, and to be so inflexible even if the person is otherwise a complete turn-on and even if the person is actively working on quitting. I'm not even sure why I am this way, but I am, and I just can't help it. I guess it's an anti-fetish.