«... What gets me is the thought that, even trying our best to figure out what's true, using our most sophisticated and rigurous mathematical tools, peer review and standards of practice, we still get it wrong so often. So, how frequently do we delude ourselves when we are not using the scientific method?»
This is the key point here. The possibility of not deluding ourselves when not using the scientific method is, essentially, negligible. And yet, I am sure that there are people convinced that their uninformed opinion is equally valid as a scientific consensus (which is not based on isolated, cherry picked studies) because,... Ioannidis.