Synge's The Playboy of the Western World reveals an Ireland in love with violence. This is the truth the play reveals. The characters in the play make a hero out of a man who kills his own dad. They put him on a figurative pedestal and celebrate his warped action. The people of Ireland have a warped sense of what to value.
And, of course, the hero doesn't even really possess courage or ability or anything of the sort. He doesn't even finish his dad off, and when the dad reappears, he cowers before him.
Ironically, the riots caused by the performance of the play weren't due primarily to the Irish being angry because they are portrayed as so violent and ignorant in the play. The riots were primarily the reaction to the swear words and rough language in the play. This, too, is revealing.
Synge reveals the truth about the Irish in Playboy just as Joyce does in Dubliners. Of course, the revelations apply to the rest of us, as well, not just the Irish.
'The play 'The Playboy Of The Western World' was not the only play to cause offence and deep anger in Ireland at the time. The new modernism in literature throughout society as a whole led to more honesty and objectivity in Irish writing and led away from the more lyrical, romantic and spiritual writing of the past with which the native population was more familiar and indeed in love with. Added to that, ireland was a very deeply spiritual nation imbued throughout with the values of the Catholic Church, at least on the surface no matter what went on behind the scenes. The new more realistic writers wanted to show true life which as always included scenes of poverty, cruelty and even vice. The delicate sensibilities of the people were outraged and saw their beloved country being sullied.