I look at it in the way of a country call up it should be total commitment to King/Queen of your country which would include singing the National anthem and taking part of any paraphernalia that the country deems fit either through tradition or otherwise. Of course not everyone agrees with this but i feel it should be a kind of unwritten rule.
In these tmes that we are in at the moment it feels that GB is in the last bastions of having all its history and tradition wiped out by a minority, so i think its important to hold on to what we are allowed to hold on to.