If you interpret your opponents beliefs as having absurd outcomes which are gravely insulting to other people, such as believing that all doctors are part of some global conspiracy, than you honestly probably are pretty bad at imagining a good counterargument to your own position. I can come up with WAY more plausible ways that a false belief could become commonly held among a profession than some sort of evil conspiracy, in fact medicine has REPEATEDLY collectively held false beliefs throughout its history so all one needs to do is draw from history to come up with plausible explanations as to why such things could happen.