"Why does the title mention Sinn Fein but not IRA in which he served longer?"
Pehaps because that's where he did his best and most positive work
Why has nobody mentioned that the people who were responsible for the shooting of 26 unarmed civilians, causing the deaths of 14 of them, still go unpunished, even though who they were and what they did has been a matter of record for forty-odd years?
Why wasn't the high-court judge who whitewashed those crimes not publicy criticised for his corrupt behaviour.   
Why weren't the authorities who were responsible for the incarceration of the six men convicted of the Birmingham Pub bombing, yet continued to keep them incarcerated for years after their innocence had been established, removed from their jobs and brought to justice for illegal detention of innocent men?
This period of British/Irish history is full of such unanswered questions.
Thanks to people like Martin McGuinness, these questions were not allowed to create a barrier to peace and reconciliation in Ireland - he got on with the job instead of trying to settle old scores.
Just as well the world isn't full of vengeance-seeking dinosaurs who are as much of the problem as the IRA or the Loyalists ever were.
Maybe I should add Brexit to the list as it stands responsible for the possibility of closing the national borders that McGuinness and his colleagues helped to open.
Looking to the near future, that is quite likely to bring the gun and bomb back onto the streetes of the North East corner of Ireland nearly as much as dwelling on who was to blame for what!
Jim Carroll