TTH, it is part of an old tradition.
"England expects that every man will do his duty"
Now we can extrapolate this to the more PC, more global world. But it is
very important especially in times of crisis to ensure that the armed forces in harm's way do their duty. Part of that military duty includes caring for prisoners according to the various conventions and laws, military and civil. I agree that it is very easy to resort to violence against a helpless opponent, but that is at the very least a failure of command. An officer is responsible for the conduct of the troops under that officer's command, at all levels of command.
As we in Britain and the US have civilian oversight of the military, it is also important to watch the watchers.
And the media reports this because it is sensational, and will generate good numbers (papers sold, news reports watched) from both the luvvies ("oh my god, the soldiers are animals") to the knuckle-draggers ("great to see those wogs getting what they deserve").