Unless you're willing to assert that, what 40%??, of the voters in the North are IRA, I say you're wrong about the second part.
"What are you talking about?? They voted for a terrorist organisation."
So, you want to take away their right to vote because you have a strong opinion of the IRA? Nonsense.
It's not an opinion, it's a fact - the IRA are terrorists, thus should not be allowed organise a political party.
People are free to vote for whatever party they want - the parties, in turn, must not be fronts for terrorist organisations in order to participate.