An interesting take on it Kona. Not sure I agree with you but it is consistent. I do see little moral difference between Mandela and McGuiness - however mandela is usually accepted as a statesman now and seen as a beacon of truth and right.
I do think it is useful to look at these people and how the way they are perceived changes depending on where you look from and when. Moshe Dayan was considered a hero in Israel in the 50s and 60s. He waws jailed as a terrorist in the 30s by the british.
Looking at history shows the absurdity of objecting to Adams and McGuiness in government now. it is the only way to end conflict like in Northern Ireland is to get all sides talking and working together and there is much precedent for terrorists to be rehabilitated and enter government.