Three replies: firstly Bloody Sunday was certainly a bloody mess, but find another military in the world who would take the shit that the British army has taken for thirty odd years in NI and have only one such incident. Israel has a Bloody Sunday every two days! The discipline shown by the army in the face of infinite provocation over such a long time is deeply admirable.Secondly if you don't shoot the Zulu or Arab who is coming at you with his bow and arrow etc, he kills you with it; the British Army should never have been there in the first place, but blame the politicians, not the soldiers. What should they have done, opened their top buttons for the spears? Finally WWI was so appalling that any attempt to make what happened then typical of the general history of the Army is absurd. Considering that the British army had 5 million men under arms by 1918, swollen from a few hundred thousand in 1914, 306 is a tiny number. I wonder how many the French, Germans, Russians shot? A very large number I imagine.
My point is not that British soldiers are saints, but that comparatively they are are a humane bunch. To go back to the song - if they are so dreadful, why the need to make stuff up? Look at the Irish, without the millions of bleating songs about the wicked British that they have, their entire folk culture would collapse.