Its possible for thr broad medical community to not be in line with the latest research (diagnostic criteria are somewhat trailing), and evidence of that would be the strongest possible support for a claim that the broad community was wrong (because it had not incorporated the latest relevant research.)

Now, sure, its useless for convincing the speaker (though not others who may be witnessing the debate) to bring out research evidence if the argument is “the medical community is wrong, and my source for that is my own unsupported belief bolstered by a conspiracy theory that the truth is actively suppressed from publication.”