Just because I quit smoking doesn't mean everyone else around me needs to quit also, unless they choose to. There will likely always be an ashtray in my house if a friend needs it and if a friend that smokes is riding in my car they will always be welcome to smoke in my car.
After all this time it still amazes me how my sense of smell now allows me to smell lingering cigarettes smoke so strongly. Even today as I walking down the hall in the building where I work, where no smoking is allowed, I knew that even though there was no one in the hallway, sometime earlier a smoker had walked down the hall as their cigarettes smell still lingered in the hallway. Just because I dont personally like the smell of cigarette smoke today doesn't mean I should treat those that choose to smoke any different then I did when I was still smoking.