This was posted as evidence of other GMs who were/are insane conspiracy theorists, and I don't think it necessarily qualifies. I have never seen any evidence for Karpov or Korchnoi holding conspiracy theory views. That, of course, does not mean it is not out there, but I have read Korchnoi's autobiography, and saw little to indicate that Korchnoi would know about let alone care about conspiracy theories - he cares about chess - and that is about it. Karpov appears to be roughly the same. The 1978 World Championship match (as well as the 1981 match between the two of them again) was a gong show. But the nuttiness was likely less a reflection of the two players themselves, and more a reflection of their team members, as well as the cold war political turmoil of a match between Karpov representing the USSR and Korchnoi who was THE defector, and an enemy of the state. Korchnoi had to leave his wife and son behind. For the second match his son was sent to a Gulag. Two high stakes matches, between two players (and their teams) who had as much distrust of the other as is humanly possible. Things get weird (part of it psychological to try to throw your opponent off) for sure. But that doesn't mean that either hold insane conspiracy theorist views.
Having said that, I don't feel that someone who holds no conspiracy theorist views is necessarily a better critical thinker than someone who holds some or even many. It depends on life experience and certainly many of the chess playing greats (Benko, Gulko and Bronstein come to mind, and of course Korchnoi. Ludek Pachman was imprisoned from 1968 until 1972 and tortured just short of death during that time) from places like the former USSR had life experiences that left them with good reasons to be susceptible to conspiracy theories.