It is not permissible for the Muslim to stand up for any national anthem, nor any national flag out of respect. Rather, this is from the evil innovations which did not exist at the time of the Prophet, nor at the time of the Rightly Guided Caliphs.
And this action negates the obligation of the completeness of Tawheed, and the purity of respect for Allaah alone, and it invites towards Shirk. And in this action is resemblance of the disbelievers, and blind following of them in their despicable customs, and deviating along with them in their extreme attitude towards their leaders and their ceremonies. Indeed the Prophet prohibited resembling them and emulating them. And the success is with Allaah. [MPAC Ireland] Read more [via Jihad Watch]