Compliments born of pity are worse than no compliments at all; they are the epitome of condescension. If someone is no good at a particular activity, at the bare minimum preserve for them that last great bastion of humanity: Pride. Do not eviscerate someone’s pride by paying that person a “compliment” that is at best undeserved, and at its worst—patronizing and demeaning. Better to say nothing at all than to pay a person a “compliment” that is transparently false or hyperbolic and makes the subject feel worse and more incompetent than they already did. A striking majority of people are not guileless and wholly oblivious to their surroundings. Thus, do not treat them as such and regale them with “compliments” that are no more sincere or deserved than a hard kick in the testicles. These people instinctually know better, and so should you.
Fred's Soapbox 