The flag flown above the bridge denotes the nationality of the port being visited, which is Honk Kong, as Hkgspotter1 says. The nationality flag of the ship is always flown off the stern. When you see a US ship in the US you see both flags as US flags, so people aren't always used to making the distinction.
Too bad planes don't have this custom!
It is not enough to be rude; one must also be incorrect.