Firstly, the Hitler stuff is nonsense. Hitler had no known devotion. He was not a Christian and seems not to have been spent much time thinking about God at all. The Nazis tried to co-opt German Christianity early on in their rule. They tried to create a half Christian, half Aryan sort of religion. But they gave up around 1936. Hitler's closest confidents - Speer, Goebbels, and Bormann - paid witness to his contempt of Christianity. Christianity and theism in general had little real role in Nazism.
And obviously, my point, if true, precisely changes the fact. Sinn Fein and the IRA have a complex relationship to the Catholic Church. No doubt there are and were devout Catholics amongst them, but Sinn Fein is a left-wing, essentially Marxist party and many of its peolpe would not be devout or even believers.
To some degree, but this isn't the same as ISIS. Some of this is also exaggerated by leftists.