Ian, Watson specifically said:

"If the behaviorists are right in their contention that there is no observable mind-body problem and no observable separate entity called mind — then there can be no such thing as consciousness and its subdivision. Freud's concept borrowed from somatic pathology breaks down. There can be no festering spot in the substratum of the mind — in the unconscious — because there is no mind."

I do not see how this can reasonably be interpreted as a methodological prohibition against talking about minds. Watson would have it that Freud's theories about mental disease are prohibited of being correct, because there is nothing there to be diseased.