Their flag wasn't hung up in a bar mate, they unfurled it to pose for a photo, the day before the game, when they went to take a look at the ground. They were then approached by Ultras who threatened them with violence unless they handed it over
@mrtwiceaseason and his lad are seasoned travellers and not daft enough to incite the locals (not that hanging a flag should ever be considered incitement FFS).
Having trawled many bars on match day, I didn't see one flag hung by any Blues anywhere. Not one.
City fans were very aware of the threat in Belgrade and adjusted the "normal" Euro away behaviour accordingly.
In fact, I would say we were impeccable :)