Sure, but that block could have been removed with Sunningdale and was mostly removed with the imposition by the British Government of direct rule and the removal of the Apartheid Northern Irish Government and even more so with the Anglo Irish Agreement yet they still thought nothing of blowing up children and pensioners.True, but fundamental to their approach was the absence of functioning democratic institutions in which to place trust and pursue those aims. The last time nationalist community tried the peaceful route through the civil rights movement they got their answer in spades.
Its a tragedy, and it is not to condone violence. It is a reality, not just in Ireland, but universally, if you block the path to peaceful protest with systemic violence then do not be surprised if people bite back.
It was only when it became politically advantageous for them that they stopped killing people, took off the balaclava and pretended that they were different people to the ones who did the killing.