The IRA, INLA, RIRA and other Marxist organizations are allied with the PLO. Traditionally though, the Republican movement has been friendly to the Jews and Devalera, the first president of Ireland, gave refuge to Orthodox Jews during WW2.
I spent considerable time in Northern Ireland in the esrly 1980s, and I can tell you that the Irish Catholics REALLY do not like Jews. The American Irish Catholics seem to be the worst.
In the Traditionalist Catholic Movement, the leaders, past and present, all seem to be Irish: Mel Gibson, Hutton Gibson, Father Denis Fahey, Father Charles Coughlin, etc.
When I was in Northern Ireland, I remember one wall mural I saw that showed an IRA terrorist shaking hands with a PLO terrorist, and underneath were the words, "IRA and PLO: One Struggle". I took a picture of that mural, but I don't know where it is now.