What we consider bluntness/stupidity is sometimes a rough optimum.
Without delicate distinctions it is sometimes better to go by the blunt rule.
Delicate distinctions allow for flexible behavior and thinkuing. SOmetimes you do that way sometimes opposite.
It is a good rule to be nice. If this is a single rule for social interactins it is good. If you are more astute, you know when to be nice and when to be strong. Even more: to be nice and strong together.
But if you do not have the ability to distinguish, you maybe actually be better off with a blunt generaliation.
There are always advatages of the blunt and simple. Less effort (unless it is easier for you to handle the effortful interesting over the boring). Simplicity has its virtues. You will also be able to act more automatically that way. Mauybe the saved attention can be used for more useful things.