I see nothing wrong with the EU placing its interests first. Indeed, I'd be shocked if it didn't try to do what it thought would be best for it.
But what's clear is that the EU and the UK don't agree on what is most important. In my opinion, the EU has come to the conclusion that economics trumps all, and everything else is of at best secondary concern. Whether that is industrial, consumer, or worker economics is but minor difference to the EU. Yet, the fact that Brexit is happening shows that for a significant part of the British electorate, economics is at best a secondary concern. The Eurocrats remain baffled by that, which no doubt explains why they think pointing out economic problems caused by Brexit will somehow cause the UK to reverse course.
A significant part but not, actually, a majority. A substantial portion of the Brexit voters were genuinely voting for Brexit for economic reasons; they believed it would be economically to their or to Britain's benefit (which could be from a left, anti-globalist perspective, an old-right imperial perspective or just general economic fuzziness). That they may have been wrong is irrelevant, except in the sense that economic arguments, both by Remainers in Britain and by the EU, may actually win some of those people back over. There are some signs now that, if a new referendum were held (not that this is likely to happen), Remain would win, after all. (Then again, that might just be demographic turnover rather than people changing their minds, given the enormous age gap in Leave/Remain voting.)
