The Black and Tans (Irish: Dúchrónaigh) was one of two newly recruited bodies, composed largely of World War I veterans, employed by the Royal Irish Constabulary from 1920 to 1921 to suppress revolution in Ireland. Although it was established to target the Irish Republican Army, it became notorious through its numerous attacks on the Irish civilian population.
It's a song of war. Those songs were IRA songs which the IRA is know in some places as a terrorist organization. Singing songs about Terrorism , which many are about killing cops is something some might have a problem.