Every nation has done things in the past of which is isn't proud. Slavery in the US, the Holocaust in Germany, the Japanese sex slaves, Cromwell's excesses in Ireland, the Albigensian Crusade in France, and many many others. History is full of these.

We should remember them and learn from them so that we don't do them again. However, this is an imperfect world and we are imperfect people (even I once had an very slight imperfection). Certain sights, smells, sounds can trigger bad old memories, memories of people and events long gone by but still alive inside our heads.

Know your audience and don't do anything to deliberately offend. "Broad Black Brimmer" and "A Nation Once Again" are wonderful songs that can get the audience "going" -- unless the audience has memories of the IRA and the Troubles recently ended (and not necessarily all of the audience).

I'd try not to cause unnecessary and deliberate pain, but the songs should still be sung. And I include the songs of ALL sides.