I have had the same thoughts myself. Several family members suffer from nicotine addiction (or alcohol) and we've watched so many die from lung cancer. I get furious over their unwillingness to change - and then realize that I, too, suffer a similar addiction.
The one challenge we have is that we cannot walk away from food & simply not eat. Cigarettes & alcohol (or drugs) are optional. I've never been addicted to any of these substances, so I can only relate to my food issues. SO HARD!
BUT - I am actively taking steps to correct my actions, I have regained much of my health by losing weight & exercising, I try not to put myself in situations that I know will cause temptation, etc. So, I guess I'm saying that I feel at least I'm trying & my family members are not. So in fact, they chose their precious cigarettes over me & my family, and they are being a poor role model for my young children.
I cannot pretend that I understand the addiction that they face - it is different for each person. I can say though that I would love to help them quit and chose life over the substance.
And then I realize that it is all I can do to stop my own distructive cycles, so the best thing to do is just to love them & let them know I am here for them.