Musar for Numbers 16:22

Another difficulty in the instructions in 16,21, to separate themselves from Korach, etc, is Moses' comment: "one man has sinned and You are going to be angry at the whole congregation?" According to Rashi G–d changed His mind and agreed with Moses (16,22). Are we to assume that Moses was smarter than G–d? Some commentators have explained appropriately that originally Moses had misunderstood G–d's intentions, and that this is why he posed the question of "האיש אחד יחטא" G–d had meant that they should separate only from the community of Korach, whereas Moses had thought that G–d had meant for Moses and Aaron to separate themselves from the entire people. This answer is not satisfactory, since we know that G–d knows what goes on in our minds. Why then did He allow Moses to make such an error instead of expressing Himself in a manner Moses would understand correctly? When two human beings argue with one another, it is perfectly normal to say that one misunderstood the other, and that this is the reason they argued, but surely G–d knew how Moses would react to His comments?