Well I am pro because of the fact that I life in Belgium and we really have a pub culture and since they banned the cigarette a lot of pubs are going bankrupt because people just don't go anymore because they hate the atmosphere nowadays The pubs smell badly ( sweat,etc...) Also I think this brings a certain amount of cosiness to a bar or a pub. If you really hate smoke in a pub don't go but I never heard somebody complaining about this for ages. Yet they changed it.
The reason is second hand smoke can kill someone. Even people who don't smoke. If smoking is able to be legal, then people who inhale second hand smoke are pretty much being murdered by smokers. Also, smokers basically commit suicide because, as everyone knows, smoking causes cancer.