I am also a smoker and I smoke a lot more than you do. I understand your frustration. When I finally stopped drinking my Doctor even told me not to worry about trying to quit smoking. He told me he would give me a year before he mentioned it again. One thing at a time. I know a lot of people who give up both, but I don't think I could have done it.
As far as those people go I try to ignore them. If they only new what I was doing to myself before, but of course they don't and I'm not about to divulge that information to a complete stranger.
Yes its bad for me, but I choose to keep smoking because I feel it is the lesser of the two evils right now. I will quit, but I'm not ready to yet.