Although the health risks of tobacco smoking are well documented, there is increasing evidence that smokers have a lower incidence of some inflammatory and neurodegenerative diseases. Many of the adverse and beneficial effects of smoking might result from the ability of cigarette smoke to suppress the immune system. Nicotine, which is one of the main constituents of cigarette smoke, suppresses the immune system but might have therapeutic potential as a neuroprotective and anti-inflammatory agent. - Effects of cigarette smoke on the immune system. [Nat Rev Immunol. 2002] - PubMed result
As with most things in life it has good and bad.
So by smoking my chances of other things is less than yours. Not saying this is a good thing, but it blows some of the more asinine arguments out of the water.