So we shouldn't research anything related to the social sciences because some people might lie about it? What leads you to believe that smokers lie more than nonsmokers if not social science research?
“It’s dark in that alley. I’d never find my keys there.”
Doesn’t matter if it’s extremely difficult to get good data here. What matters is we can’t substitute bad data if that’s all we can come up with.
And although I stated it as smokers lying, the implication is that the nonsmokers are lying (by claiming to smoke).