Can't really recall any. But then I just avoid people who are likely to annoy me and try not to dwell on it. It's like 2nd nature now. Also helps to do due-diligence beforehand, so I can provide my context and targeted questions from the get-go.
Funny enough, I've encountered a couple big dealers via Facebook friends - not for audio related business - who turned out to be real sh*t-heads. Fortunately there are PLENTY of dealers and manufacturers I really do like. And I've maintained a good relationship with my main dealer for some 15 years.
So, no problems with bad salespeople here. If anything, it will be entertainment if/when it happens.