I've never had someone be really rude to me. My worst experience (mild as it is) was when a well-known dulcimer virtuoso agreed to judge an informal contest at a music festival a few years back. He's not a rude person but he's known for being self-centered. All of the entrants were pretty green, but the point of it was mostly to get tips on what we needed to work on. I was one of the better players so I played two tunes that I had been practicing for less than a week. I know I did pretty poorly--my timing was awful, I flubbed a LOT of notes, and I forgot part of one piece and had to patch it together (and it was definitely noticeable--I think he even knew the tune). He placed me first and said I sounded fine and didn't need any pointers. He hadn't been paying attention to anybody's playing and he couldn't offer any advice beyond "keep practicing", which he told us as if he were bestowing some wonderful secret on us. It was insulting.