The Duning-Kruger effect evidently exists. This post is not an attempt to debunk it: rather, it’s a plea for DK not to be abused.
Anybody and everybody can use a variant of the following: “Since you are not an expert in the field, your skepticism about it is derived from you overestimating your own knowledge about it“. Such an argument “provides poor reasoning in support of its conclusion” and therefore can be classified as a (material) fallacy (in particular, as an example of “Affirming the Consequent“).
To understand the above, imagine that any “expert” in homeopathy, in UFOs, in chemtrails will of course be able to repeat the same argument against any skeptic, for the simple reason that few if any skeptic will have devoted their lives to the study of homeopathy, UFOs or chemtrails.
Why, if the DK argument were valid, we would all be forced to believe in all sorts of religions, since it would be impossible to know more about the Bible, the Qu’ran, the Mahabharata more than respective (believer) scholars!
There could be many reasons not to believe in something. The abuse of the DK effect as a DK argument is just a naive case of “pop psychology“.