I was giving that verse as a possible reason why virtually no-one in Scotland sings the "National" anthem. As a schoolboy in Wales for a few years I myself found it a little strange when returning to Scotland that at times like the end of cinema performances when the anthem was played, instead of standing everyone made a mad scramble for the exit. I don't know if people still stand for the anthem in Wales but this was over 40 years ago and it is many years since I have heard it played anywhere other than on TV.
I can't say I find "Flower of Scotland" a particularly apposite anthem and would much prefer something like "The man's a man for a that" which reflects more closely the Scottish attitude to those who seek to set themselves above others by a mere accident of birth.
Any English flags flying in Scotland would no doubt belong to English people who had moved here. I have to admit feelings of antipathy to see such a thing in my country although I would never contemplate the sort of action taken by others to remove them and damage property.