Eh.... I reread my posts in this thread, and somehow they all sound like libertarian agitprop to me now. I didn't mean them to come out this way. My main concern is a different one: I'm getting a sense here that you, Dasha, are worrying too much about problems that needn't be yours to worry about.
Your college already gives your students plenty of opportunities for socializing in a smoke-free environment. It provides a friendly atmosphere where nobody has to stress-smoke (which is what Green Witch's cutting would be a parallel to). A mere month and a half into your new job, you're contributing yet another alternative, your film club. Having met you in real life, I am certain that you're making the college's friendly atmosphere even friendlier. So nothing you do encourages them to smoke (except, possibly, the example the faculty sets). And many things you do already encourage them not
If, in spite of your efforts, your students still choose to smoke, I think there comes a point where you just need to let go and leave good enough alone. A point where you need to remind yourself that you are not their mom and they are not teenagers anymore. They are grown-ups who can make their own mistakes and learn from them. Don't let your concern for their health get the best of you after you've already done more than your job.
Does that make sense?