Personally, I find that I am always nervous when dealing with public servants (salespeople, bus drivers, etc.) and it shows in my speech and... possibly facial expression... when I communicate with them. They haven't really abused me like yours has, but they seem to look down the nose at me.
Just for some suggested advice, to prevent yourself from feeling bad about the situation, maybe when these salespeople make you feel bad or do something that is uncomfortable for you, you should speak out about it! Politely ask them not to make physical contact with you, etc., because you don't like it, and if they persist you could consider consulting the manager of the establishment who will do something about the worker's behaviour, or just leave. All the same, I hope that you never have to experience a situation like this ever again! It must've been mortifying.
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I used to plan and plot, and try to live correct; lately I do a lot of things that don't make sense. Now I must do what I must do.