In every country it is normal and an emotional moment if the players of the national team sing the national anthem. Just the "German" player with roots in Ghana, Tunisia and Turkey as well as Polish Lukas Podolski refuse to sing the national anthem. Would be okay for me if they weren't in the National Team!
In my opinion it should be a MUST for players to sing it, otherwise they'd have to stay out of the games. That easy, I think.
Would you accept someone playing for your country who refused your anthem? I'd like to see your opinions.