Re: Belt color importance
About the original post:
Sorry, but to me your behaviour seems equally rude as the guy's. I'd never, ever go around correcting random strangers in solo practice at seminars. Maybe (just maybe) when we train two on two and my partner is either doing a grave mistake continually or is just a confused beginner, I might make a humble proposition ("You know, I think it might work a little better if..." "Didn't sensei show it like...").
But in single training, a guy I've never seen before? Sorry, but there the only one supposed to correct me is the teacher. Or maybe someone from my dojo that I know. Or my teacher. But definetely no strangers. And that's not depending on rank at all...
(Although of course the guy was rude - I tend to go with "smile and ignore"...)
Anyway, we don't really have the belt colour issue here in Germany (or Sweden, or France), as it's mostly only black and white, apart from a few organisations we don't really have a lot to do with.
We do wear a hakama from second kyu though...