I think that if a team has a contingent of multinational players that see their own national flag then it makes them feel honoured and accepted. Having flags at a game has always been part of the game hether it is club national or the flag of the country a player comes from. Its not to wind the opposing fans up it is to honour the international player(s) in the team they support.
Besides on a dull wet Saturday afternoon it adds a nice bit of colour.
