Example: a friend of mine moved to a new country (Central-European capital to large city in Western Europe). At some point he was in the pub with a bunch of colleagues, and he asked one of them who had obvious accent about where they're from (they were a person of color). They asked back 'what do you mean?', and apparently got very offended.

The funny part: for my friend, who also had a strong accent, it was odd (and not very nice) if someone didn't ever ask about where's he from -- because he was obviously an immigrant.

Just telling this story because something that can possibly be interpreted as 'racism' is 'basic niceness/politeness' for someone else. If we're celebrating diversity then let's embrace it properly.

"something that can possibly be interpreted as 'racism' is 'basic niceness/politeness' for someone else. If we're celebrating diversity then let's embrace it properly. "

Thank you for your wisdom. I have been saying something along these lines for a long time, but never so eloquently.

While unfortunate, I think this just shows it's a little unwise to ask such a thing in today's, often xenophobic, society. I can't attribute malice to me being asked that question, but I'm white, middle class and British, so I don't have any bad experiences to be wary of. Perhaps the person being asked was used to that kind of question having rascist undertones, perhaps the conversation prior to the question had affected the context, or perhaps your friend's tone was unintentionally abrasive. I'm not suggesting any of that is what happened, but it only takes a little to blow something out of proportion.

What people also don't talk about is how difficult is this for people with autism or Asperger's. So there are these rules about what to do and not do that are extremely complex, and people can't rely on their genuine intentions. The friend in the story is has some minor autistic traits while he's very intelligent and social 'otherwise'.

And being told they offended someone hits hard. They never got the memo that the question would be inappropriate, especially that given their own accent, they have been asked the exact same question.

Why is there a rule all of a sudden? Why did I not get the memo? Why was it okay for others to ask me but not me someone else? Is there a special exception for this person? Is this a national culture thing? Can I fix this? I didn't mean to offend but I did!

That's what would go on in my head. I don't think that's unreasonable. If you want people to conform to your social or cultural norms, you need to explain them first.

And as is mentioned in the comments, assume good faith first. Educate instead of judge. Live and let live. Was there harm done by the question?

Americans often get asked about ethnicity / roots in Europe and they take quite an offense even though people are just curious and find it interesting and good topic.

I think this is missing the point. It's to assume good intent when interpreting whether something is racist or sexist, not assume good intent when deciding how to react to racism or sexism.