If there is much greater variance within populations than between them, then it is foolish to make decisions about people based on their race, as it gives very little information about them.
All you say is true, but it won't necessarily save you from the Thought Police. For example, the variation in strength within male and female populations is bigger than the variation between them. It may therefore be foolish to make decisions based on gender rather than on strength when hiring, say, dockworkers. But when people complain about how few female dockworkers there are, what will you tell them? Mutatis mutandis.
All you say is true, but it won't necessarily save you from the Thought Police. For example, the variation in strength within male and female populations is bigger than the variation between them. It may therefore be foolish to make decisions based on gender rather than on strength when hiring, say, dockworkers. But when people complain about how few female dockworkers there are, what will you tell them? Mutatis mutandis.