There's fairly lengthy article in Foreign Policy that attempts to explain why the Irish have been supportive of the Palestinian cause, actually its champions in Europe according to that article. The argument/explanation goes along a combination of factors from the Irish identification with the [most] oppressed to the "Vatican factor". The article also says that in contrast, Great Britain "has always been viewed as pro-Israeli", but it's not terribly clear if by this it means its foreign policy or public opinion. At least in recent times, the UK public opinion doesn't seem incredibly sympathetic to Israel (in that conflict), but it's conceivable that the Irish public is even less so.
Corroborating the picture of the Irish being pro-Palestinian, an article in the Economist paints the Ulster unionist parties (DUP and UUP) as the most pro-Israeli in the UK, e.g.
In 2014, when the British House of Commons voted on the principle of recognising a Palestinian state, five of the 12 “no” votes came from the DUP.
while Sinn Fein being on the opposite end, with the IRA having a history of some cooperation with Palestinian armed groups.
But Northern Ireland is not quite the UK, so I wonder if comparing the UK as whole with (The Republic of) Ireland have there been significant differences in public sympathy toward Israel, and if so in what time frame? (E.g. did these differences diminish in the aftermath of the Good Friday Agreement?)