Who do they want to country back from?
I think there is a sense that we are losing our English indentity and it would be foolish not to recognise the immigration issues.
Parts of our major Cities are irrecognisable from a generation ago and that is likely to cause some discord.
The march has gotta be totally legitimate and neednt be dismissed by those that can't help to offer themselves up some sort of liberal superiorists, whom themselves get it wrong so very often !
It didnt surprise me that your first two ironic examples of who they might want it back from were:
Middle Classes and the Literate.
Of course implying that those who might not agree with your own liberal views are of course ill educated and bound to be poor.
Not much prejudice there then !!
Yeah the singing was boorish and probably there were some with their own extreme agendas, but the sentiment is likely to be shared by many.