A lot of it can be attributed to the dilution of our national culture, why should someone who determines themselves as being of different origin that English give a sod how much the English are denigrated. FOM in particular has been a great tool for the EU to depopulate the main 3 countries of their population by bringing so many more people in who aren't from their cultures, this has a knock on effect of strengthening the EUs hold on those countries because there are less indigenous people in those countries to fight back.
Scottish independence is fine, and let's all stick up for the Irish and the Catalonians, but the English are just little Englanders and we need to sneer at them at any given opportunity, it's no shock to me that those doing the sneering tend to be the people who support Labour, remain and Ironically Harry over the throne.