I'm looking for the first people/studies that came out and said smoking = bad. It seems weird to me that anyone could think inhaling smoke was a good thing.
I looked at old questions and found this - http://www.reddit.com/r/AskHistorians/comments/1wcwgy/was_it_actually_agreed_by_many_doctors_that/
While the first answer seems good, there are no sources.
Secondly, what was the opposition of people like. Psych 101, would say that people exhibit dissonance/reactance, and not believe this information - was it akin to how people react to climate change?
I'm also interested in whether the use of doctors in ads, was a direct combat to doctors/researchers becoming more unanimously against smoking?
Partially answered my own question:
Lung cancer was once a very rare disease, so rare that doctors took special notice when confronted with a case, thinking it a once-in-a-lifetime oddity. Mechanisation and mass marketing towards the end of the 19th century popularised the cigarette habit, however, causing a global lung cancer epidemic. Cigarettes were recognised as the cause of the epidemic in the 1940s and 1950s, with the confluence of studies from epidemiology, animal experiments, cellular pathology and chemical analytics. Cigarette manufacturers disputed this evidence, as part of an orchestrated conspiracy to salvage cigarette sales. Propagandising the public proved successful, judging from secret tobacco industry measurements of the impact of denialist propaganda. As late as 1960 only one-third of all US doctors believed that the case against cigarettes had been established. The cigarette is the deadliest artefact in the history of human civilisation. Cigarettes cause about 1 lung cancer death per 3 or 4 million smoked, which explains why the scale of the epidemic is so large today. Cigarettes cause about 1.5 million deaths from lung cancer per year, a number that will rise to nearly 2 million per year by the 2020s or 2030s, even if consumption rates decline in the interim. Part of the ease of cigarette manufacturing stems from the ubiquity of high-speed cigarette making machines, which crank out 20 000 cigarettes per min. Cigarette makers make about a penny in profit for every cigarette sold, which means that the value of a life to a cigarette maker is about US$10 000.
The earliest I am aware of was when James VI of Scotland/James I of England wrote A Counterblaste to Tobacco.