Regardless if Karpov was a recruited KGB informer or not, he behaved always fairly and politely towards his chess opponents.
Korchnoi lost his matches vs Karpov simply because he was the weaker player of these two. That was the most decisive factor: not yoghurt, not Zukhar, but the actual ability to play chess over the board. Brezhnev and Baturinsky may have preferred Karpov as champion, but they would have been powerless to prevent Korchnoi becoming a champion, if he had played better than Karpov. Extreme measures (ie murdering Korchnoi) were out of question, for many reasons.
Petra Leeuwerik's behaviour in Baguio 1978 was just inappropriate.
ISIS leaders and their heartful ally.