I had one this evening - was in the right but leaves me a bit...jumpy.
Having a meal in our local but the table next to us got completely out of hand. A group of those upper middle class types that wear a blazer and "fun" shirt on a day off and talk at a volume where everyone within 100yds knows every intimate detail of their lives and they just don't care. Add a load of booze and the volume was so loud there was no way we could talk without shouting (in a quiet country pub). Turns out they don't like it up 'em and a polite "turn it down a bit please" is considered a declaration of war. Apparently they have never been spoken to like that before and I'm an utterly ghastly man. Luckily the landlord and staff know me and they were shown the door (although fisticuffs could have been amusing and strangely satisfying). A pub full of grateful punters and a very apologetic staff largely puts your mind at rest you were not wrong but you still feel an arse for becoming the talking point of the night.
Normal middle class & the proper, proper posh - mostly polite and considerate. But that group in between - what a bunch of cocks!