It's worth keeping in mind when people wonder how there could be so many people who reject certain scientific findings. A lot of the time it's a similar attitude - "I'm not going to bother looking at the studies, but I'm guessing the people who studied it didn't think of the problem that immediately cam to my mind, and as such their results are probably wrong."
Annie Duke talks about this in her latest book.
Then there are things like https://en.wikipedia.org/wiki/Parameter_identification_probl... and whole books like https://en.wikipedia.org/wiki/Causality_(book) examining the problem and its' difficulty.
Can you explain what you mean?
It's just a reflexive response for some people at this point.
Edit: having said that, yeah, I don't have any actual research experience, and the data does look pretty convincing - as in, banning pesticides probably does contribute to a reduction in suicides a non-trivial amount.