A 'blunt' statement is when someone says things to the point and factual. But wouldn't 'sharp' (or some other word that implies frankness or sharpness) be a better word than 'blunt'? As blunt has the meaning that it is not sharp. When someone says something that is not direct or something soft (and if I am to make phrases or rules in English) then I am more likely to use 'blunt' for such a thing. All I am saying is the real meaning of the word is not appropriate(actually opposing) for the phrase. Being direct is never 'soft' and can hurt and blunt real meaning is more close to 'soft' and cannot hurt you (compared to a sharp object).

Blunt dictionary: (of a cutting implement) not having a sharp edge or point. "a blunt knife"

(of a person or remark) uncompromisingly forthright. "a blunt statement of fact"(of a person or remark) uncompromisingly forthright. "a blunt statement of fact"

Etymology here points to some interesting meanings and usages but none quite explain the usage in phrases