The logic of believing that all smokers smoke 20 a day, all smoke in bus shelters or outside shop doors, and all smoke around their DC is about as sound as believing that all drinkers drink a bottle of wine a day, drink on the street and get drunk in charge of their DC.
The majority of smokers I know, myself included, are well aware that it is a bad habit and one that non-smokers dislike being around. The majority of smokers I know smoke in their back garden, don't smoke around their DC or their non-smoking friends, have smoking coats/clothes, wash their hands and clean their teeth after each cigarette etc.
I suspect that this 'rough, nasty, gormless' impression is because of a limited impression of smokers posters have seen in public, and they are then applying that to everyone.
You can dislike smoking as much as you want, that's your right, and I'd be the first person to agree that the smoking ban was a great idea and has made pubs and restaurants a million times better than they were. Just don't tar every smoker with the same brush. Plenty of smokers follow current guidelines/advice about restricting second-hand smoke and will only have it as their (legal) treat in the evenings, or on a lunch break from work.