This is typical of cult thinking, in this case a Marxist cult. They assume anyone criticising them is wrong (and a conspiracy theorist) and also that they are wrong even if they are factually correct. This is because they are ideologically wrong, which in the Marxist cult is the worst kind of wrong. This is outlined in Herbert Marcuse's essay Repressive Tolerance. It is not possible for an ideological opponent of a Marxist to be right in their eyes, they aren't even considered to be people (a partof "The People").