Say What?

"HEY SIR!" I look around. I am just minding my own business walking down the middle of the street during a music festival checking out the vendors. Following the crowd. No uniform or distinguishing t-shirts as I am way off duty, and enough people at this fair recognize me anyway from various classes I have taught or jobs we've worked together. Hearing somebody calling to me is not unusual today, but hearing somebody call me "sir", means they don't know me. (I get called lots of names, nick-names, and 'other things', but "sir" is not one of them.)
I turn and finally identify the hailing party, a young man, probably mid twenties, giving me the thumbs up signal and he says "nice mustache sir!". His buddy nods in agreement and says "yeah man, we're working on it too!" and he strokes the close cropped hairs surrounding his mouth. I give them a wave, mumble something, smile, and keep moving.
The truth is, I'm speechless and don't know how to respond. They struck a staggering blow to my self esteem without even aiming. Facts: I am not a pretty guy. I have never been concerned with my looks and I know there is nothing special about me. I keep myself properly groomed and acceptable, but flashy haircuts, slick clothes, cologne, and things like that don't enter into my thought process. Also, for the new reader, please note that I am not a youngster and have been happily married for many many many years. I really get thrown when somebody makes a comment, good or bad, about my appearance. It reminds me people are LOOKING at me and I don't like it much.
My mustache is really nothing special. Some call it a funmanchu, but the fact is that it is grown such that it leaves my chin just above the jaw line and hangs down about 3 inches. I shave up and under it every morning to make sure the connected hairs don't get over the bone line. This is so that my SCBA mask goes on and makes a seal without interference. The 'stash just gets shoved up inside the mask. If it gives me a problem, I can cut it clean with a single hack from my trauma shears. My version of practical. No body seems to notice this except for a few friendly comments at work and some of my younger crew mates who joke about getting a hold of it to make sure it's real. I invite them to try if they want that to be the last thing they ever do on this earth, and we all chuckle. But having somebody pick me out and choose that to make note of is disarming to me.
It's only happened once before. About 2 years ago I attended a lecture presented by Chief Billy Goldfedder. During the break I went down front, introduced myself and told him how much I was enjoying his program. He looked up and said "hey, nice 'stash!". I think I blushed, I KNOW I was embarrassed. If you know the Chief, you know he sports a thick, heavy, well trimmed mustache. Mine is skinny, scrawny, spindly, and funny looking. I completely forgot the point of my attempting to speak with the Chief, thanked him again, and wandered off.
The young dudes who called me out yesterday threw me off and now I'm really wondering why. What's wrong with me that I can't just accept a nice comment and move on? Perhaps it's because I don't hear many nice comments and rarely take them seriously.
Maybe I should just cut the damned thing off and forget about it.
UU