I don't think people are saying that it cannot happen, just that you need to prove it instead of hurling empty accusations, especially when it can destroy someone's career. I personally think it sets a bad precedent if every top player immediately starts crying "cheating!" when beaten by a lower ranked one.
Surely he means just that; i.e. Hans Niemann is known to have cheated in past games (these were online games and it must be noted that Niemann maintains that he has never cheated before or since the and never in an "over the board" tournament).
