Re: Belt color importance
We use colored belts at my dojo starting at 7th kyu (yellow). 2nd & 1st are brown. I think it helps in the beginning to get newbies motivated. After a while it doesn't really mean much but it does make a good motivational tool in the beginning.
As far as the A hole asking you if you are a fucking sensei...LOL, wow, bad attitude, just broke up with his significant other, who knows. Impolite and disrespectful? Sure. Worth loosing sleep over? No. I would just assume he was in a bad place at the time and let it go. If he was at my dojo then that would be a different story. Since it was at a seminar I would just let it go.