Well, I wouldn't call it "supporting" both sides.
I have nothing but the greatest affection for the Irish culture and civilization (which, as might need pointed out, pre-dates other European culture and civilization, including that of the English), but on the other hand, am puzzled that so many Irish, and Americans of Irish derivation, sympathize with a terrorist group whose purpose is not Irish-ness, but socialist totalitarianism.
I wish nothing but the best for both of the countries and I don’t think trying to create an artificial Northern Ireland state is realistic. It is part of Ireland though.
I don’t sympathize with terror groups... although if I were around in the mid-1770’s I bet I would have sympathized with those colonial subjects in North America!