Jim,
Your father was lucky to make it back.
My father's brother planned to go but was prevented by family pressure.
(and I too believe in learning songs before performing them)
You are right of course, that the harsh capital punishment meted out to the Easter rebels finally brought popular support for their cause.

I do believe that there was a moral justification for Britain and France to defend themselves from The Kaiser's armies, as did those who volunteered to fight.
Conscription did not come into force until 1916, and was never used in Ireland. The white feather campaign was not state instigated.
My grandfather was given one on his wedding day, 2nd June 1916 although he must have been in his naval uniform. It may have been the popular impression that the Navy had failed the nation at Jutland.
Keith.