So, as for the prawns being considered stupid drones, I don't really think that. I think the parallel they were trying to draw with the scientists "theorizing" that the prawns were all drones to notions of racial superiority. The prawns have no initiative because they were slowly forced to live in slums. The humans then theorize that the reason these slum-dwelling creatures have no initiative is because they are genetically inferior to them, and continue to oppress them. This is really similar to the treatment of racially imposed slums, where the leading thinkers of the "superior" race declare that the oppressed race is inferior, and cites as evidence, "Look, when we through them all in slums and exploit them, they don't care."