“The rancor against Britain ran deep, perhaps because of the Irish Potato Famine.”
It goes back farther than that, at least to Cromwell’s conquest in 1649 and the establishment of Ulster.
Not all that different from the Irish raids for loot and slaves on England and English counter-raids, back in the day. Heck, the same kind of thing happened with respect to Scotland and Wales. The famine was a different animal, simply because the death rate was an order of magnitude bigger, and England could have done something about it, via food relief.
Bottom line is: you can’t claim to be the sovereign power, and not provide succor in a time of famine. Wartime atrocities (which both sides engaged in) are one thing, but standing by in peacetime while mass death from famine occurs in a time of relative prosperity - in a territory that’s part of the realm - is quite another.