I agree with Rick regarding singing songs of this ilk, be sure of your wherabouts, if in doubt sing something else. I once played in a group caled " The Foggy Dew" but we did not sing this song or any other like it for fear of causing grief, there are hundreds of great songs around, better to stay clear of political ones unless your are sure of the audience. BTW, the original Foggy Dew is an English love song ?.Also if you do get to read the books by Tim Pat Coogan as suggested by Big Mike and Fiolar, try also to get your hands on one by Michael o Cuinneagain titled " On The Arm Of Time" for a more balanced look at this period in Irish history. There is lots of evidence to show that De Valera and Collins were always very good friends even to the last, There is also evidence that Collins may have been blackmailed by Llyod George and Churchill to accept the terms of the treaty for fear of blackmail, as it was rumoured that Collins had an affair with an English socialite and may have fathered a son by her. There is also evidence that both Collins and De Valera may have been having meetings with British agents believing all the time that they were republicans and also that it may have been one of Collins's closest friends, (who in reality was a Secret British Agent) that fired the shot that killed him, This evidence is cicumstantial but O'Cuinneagain goes into such detail, and quotes so many sources that it raises genuine questions about the historical facts of that time. Again don;t be afraid to ask, someone will always answer.
Good luck