Joke and insult aren't mutually exclusive categories. 'Taint nothing wrong with it among comrades who have the established rapport to contextualize a little ribbing, but for outsiders to use it is mighty presumptuous. A fellow soldier might someday earn a Purple Heart, but some sideline civilian isn't ever, and that give the same words from civilian mouths a nasty edge of "what you can have and we can't, we'll run down".

I mean, saying, "Oh, it wasn't anything," oneself, is humility. Saying, "Oh, it wasn't anything," of someone else, is a put down.