Anyone who believes any study involving smoking over the last 20 or 30 years should seriously question the source. Let's face it, inhaling smoke is bad for you, no question about it. The more you smoke, the more damage you're causing, just like the more caffeine, sugar, fats, etc. you consume the worse it is for you. This doesn't take massive research to prove, everything you do has consequences just as everything you don't do has consequences.
Most of my life I did a lot of rather unhealthy things including smoking. I also did a lot of healthy things like getting a lot of exercise which seemed to counteract a lot of the harm I did. Would I have been better off never doing the unhealthy? Probably, but maybe I would of bored myself to death by now.
The way I look at it, I lived my life the way I wanted to and as I get closer to the end I have few regrets. More importantly, I let others live their lives the way they wanted to without passing judgement and that to me is more important. It's a shame that there a few among us that feel we all have to take this journey along the same path.