It's raising children to think they must be 100% patient and polite at all times, even in the face of rudeness, which puts them in vulnerable positions.
I read a good blog once that said the way we raise our children to be polite and tolerant means they get trapped into things they don't want. It was a rape blog so it was obviously geared more to that, but I think you can apply it to this situation.
Children are taught to be polite at all costs, which sticks with them for the rest of their lives, meaning we find ourselves in positions throughout life where we are trapped in situations purely because we're afraid of offending others and being rude.
I can think of dozens of examples when I used to go out with my friends to pubs or clubs. Not a single time have I been out and not been cornered by a few much older men flirting inappropriately with me and making me uncomfortable, and yet I am always too "polite" to say fuck off and leave me alone. To the point where I've felt forced to give out my phone number to the strange men who want me to "come to their house around the corner with them - just as friends, honest - no sex" just to get them to back off without being "rude".
It applies here because similarly I've even gone to a GP appointment with something important to talk about and ended up backing down very quickly and leaving before anything was done about it just because I thought it would be rude to say, "No, you're my GP and there's something wrong with me which can't just be dismissed."
OPs nephew was not rude. He was determined and true to himself, and he didn't allow himself to be pressured into suffering just because someone older than him was rude and dismissive of him.