I think Pickled Onion's take on it was a bit wider though and felt to be a bit more impactful on him personally, as demonstrated by the other story he linked to.
Yes.
Obviously the "really" question is offensive regardless of context or even race, it's basically "are you lying to me?", the race element makes it 100 times worse.
I was a little surprised at both the reaction of my breakfast companion, and the linked article, where it seems you shouldn't ask a person where they're from if they're black. I am upset by the fact one should discriminate - so it's fine to ask someone white with a northern accent where they're from and get the answer "Bradford", but not someone non-white where the answer is the same.
Reading through the replies, it seems this is a very British problem, and is clearly due to the number of racist bigots we still have, so that people come to see the question as hostile through constant repetition.
As Flatus says
It's an awkward one, because I too am fascinated by other people's cultures and it is largely what drove me to visit 50+ countries. But I'm also aware that unsolicited enquiry may not be read in the way intended, in the context of UK residents facing media driven hostility.
Most people everywhere you go are interested where you come from, and are quite happy to reciprocate, being either proud of where they were born or grew up or of their ancestry and will be keen to talk about it. It seems that in Britain there are a lot of people who despite being British feel they are not accepted as British. That may be media driven hostility, or the media reflecting attitudes (certainly not attitudes of circles I am in contact with) but either way it is sad and concerning.