It’s a rare feat, according to Ben Schwarz:
Most men’s obliviousness to charm supports the proposition that the quality is not essential, even as that obliviousness makes for a decidedly less pleasant world. Charm is a social—a civilized—virtue. But its very refinement, the weight it places on self-presentation, means that it is inherently manipulative.
All of [Cary] Grant’s characteristic winning expressions—the double take, the cocked head, the arched eyebrow, the sideways glance—signaled that he was pulling something off. The charming man (or woman) always knows that he (or she) is pulling something off, no matter whether that charm is used to put the wallflower at ease, to get the soccer dad to exchange some pleasantries, or to close the sale. The charmer knows that he or she is manipulating—and in the end, it’s impossible not to be at least slightly contemptuous of the object of one’s manipulation.
The Dish 