Cui prodest? A volte anche solo allo scambio di idee

I think Hannah Arendt said that one of the great achievements of Stalinism was to replace all discussion involving arguments and evidence with the question of motive. If someone were to say, for example, that there are many people in the Soviet Union who don't have enough to eat, it might make sense for them to respond, "It's not our fault, it was the weather, a bad harvest or something." Instead it's always, "Why is this person saying this, and why are they saying it in such and such a magazine? It must be that this is part of a plan."