Watson’s general comment about Africa policy was true when he said it and remains true today.
We can debate why it was true—given the obvious wide variety of people who live in Africa—but his point deserved serious discussion instead of banishment and turning him into a non-person for daring to have the discussion.
Indeed, and it now applies rather sadly but nicely to inner cities in our own United States courtesy of teachers' unions and grade inflation and tests showing reading and math scores dropping precipitously. So something unifies these, one might argue.
---- "...his point deserved serious discussion instead of banishment and turning him into a non-person for daring to have the discussion."
A well-taken point, and the parallel to turning over the chessboard before your opponent checkmates, or in shouting down when arguments' logic fail. Ergo the recent "cancel culture" games, which are essentially about avoiding reasoned debate relying on reasonable sources.
---- "Our language is imperfect—and much of what is taught in school is an oversimplification of a ridiculously complex real world."
A fair observation, we'll agree. Oversimplifying makes for easy lessons, and easy lessons come to be hard lessons in the end.
--- "That does not make generalizations useless—but they are most valuable when used with proper care and disclaimers as appropriate."
Herein we might see things differently. The kind of manipulative politics we have seen from the Left speaks specifically to your remark. The intention of generalizations in their ruthless hands is that they NOT be "used with proper care and disclaimers as appropriate."