This makes me far from happy. Several of my friends, or at least acquaintances with whom I get on well, are among those five million. Quite a few more may be UK citizens now but were not born so. And some are no longer living in the UK because current UK immigration law, even before any Brexit-induced changes, made it impossible for them to establish permanent residence here. Some of them are here on LJ. Interestingly, some in each of these categories are both white (at least to all appearance) and non-European - not fitting either of the current British migrant stereotypes. That does not make the situation better, except possibly personally for them - in fact, it probably makes it worse, as so many other people who are seen as fitting one of the stereotypes has had to be coping with increasingly repeated abuse.
Was the decision democratic? Perhaps, perhaps not. Precedents within UK electoral practice can be found for both citizenship and residency as a determinant, with the more common one probably being citizenship. And the decision to use citizenship this time was explicitly taken, so it at least followed the accepted rules - at least so far as what was officially being voted on is concerned. So, at any rate to that extent, it needs to be accepted - particularly as people, not just in the UK or even in the EU but throughout the world (including any currently-inhabited satellites), need some certainty as to which decision has been taken. Any usable acceptance of reality relies on mutual trust. But intolerance of others was not a matter that was supposed to be part of the agreed question - and any attempt now to suggest that it was must be firmly rejected.
I have more to say, almost all of it deeply discouraging, about post-referendum politics in Britain and the prospects for withdrawal negotiations - if I can find the time, the words and the will. But that had better be it for now.