What
oryx said
Yes it is, like the dismissal of millions of people living in the north as racists is much more than annoying.
"Left behind"* communities can be found all over the UK.
People from all over the UK voted for Leave, even in London you had a Leave vote of 40%. And they voted Leave for all kinds of reasons.
There are strong majorities in this country for more restrictive immigration policies (and the size of those majorities indicates that they must include significant numbers of Remain voters). There are also strong majorities that are appalled by the Windrush scandal (and again the size means there must be Leave voters in this majority), even though it was the former that led to the latter.
The catagorisation of people that have voted Leave, who are concerned about the impact of immigration, who have voted UKIP as racists has only benefitted the hard-right. A small minority of people are ideological racists, the rest of us, whether we voted leave, remain or abstained, cannot and should not be categorised as racist or not racist.
*hate that phrase, these communities weren't left behind they were systematically attacked.