Why the hell would someone do this in a music store?

A couple of days ago on Friday, February 4, 2011 I was playing music on an electric piano in a music store. I was playing very well, and a lot of people complimented me on my playing. I played pieces such as Waltz in C Minor, the Revolutionary Etude, Grand Valse Brilliante, Moonlight Sonata, the Minute Waltz, Fantasie Improptu, and The Dream of Autumn. I was playing the beginning of Chopin Waltz in C minor, and playing very well and expressively and not too loud, and this guy comes up to me, yells in my ear, and says, CAN YOU TURN IT DOWN? I told him to get away from me after turning it down. He started walking away, and I said, Next time at least ask me in a nice way to please turn down the volume. He gave me a dirty look. Why do people feel the need to insult someone who's good at piano in a disrespectful way? Is it because they are jealous of them? A few minutes later I was playing the Minute Waltz by Chopin and this worker in the store comes up to me and says in a very loud voice, TURN DOWN THE VOLUME! People are trying to work here. I told her to go somewhere else because she should mind her business because I WAS NOT playing loud, and many people complimented me on my playing. Then she said, EXCUSE ME? I "love" your playing, but you need to turn it down, even after I turned down the volume. And then she started walking away because she knew she was wrong. I raised my voice and said, Next time it would be nice it you could ask me politely to turn down the volume instead of coming up to me and yelling at my ear and talking disrespectfully to me. But that's besides the point. Why do people feel the need to insult someone who's good at something. Is it because they are jealous of that person? Also, who do you think was right in the situation with the women who criticized how loud I was playing? It was her tone of voice that really annoyed me, along with her saying I was playing too loud when I wasn't even playing loud. I was playing the first portion of the minute Waltz very enthusiastically, and she had to say I was playing too loud when I know I wasn't. What are your opinions on this? Thanks.