Mr. Vanderboegh points to an article that claims opposition to authority is a form of mental illness.(which is based upon the same source as the first article about internet habits; the American Psychiatric Association's Diagnostic and Statistical Manual (5th edition) which was released in 2013.
Chipping in my 0.008 Drachma's, I stumbled across something else. The very weak and complicated links between mental illness and gun violence is an article concerning a study entitled Mental Illness, mass shootings, and the politics of American firearms (.pdf). Not exactly a pro-gunowner take on things, but it does refute the idea that all folks with mental illnesses are dangerous and it could provide some defense against the notion that background checks should be expanded to catch the mentally ill as they're not that much of a concern..
Now all of these together should make the notion of using mental illness as a disqualifier for firearms ownership a problematic and troubling proposition. If the definitions in the DSM-5 that are mentioned above are used, then we could all very well be "the wrong people".
For the halibut, below the fold will be a probably-not-safe-for-work director's cut video from our favorite rock star machine gun owners and the music video debut of Arwen Undómiel.