"While there is little evidence that gerrymandering seriously affected the vote in Parliamentary elections as much as the abolition of PR almost certainly did; the manipulation of local government boundaries is much more firmly based - there are instances of Nationalists losing control in a number of councils where they had a majority of electors."

There was also an instance where a unionist majority of electors saw Nationalists have control. Hence it depends on who votes and who doesn't and it also depends on the assumption that every single Catholic would vote for a nationalist and vice-versa. There seems to be no doubt that discrimination went on but it also seems to have been somewhat exaggerated by some for political purposes.

http://cain.ulst.ac.uk/issues/discrimination/whyte.htm

It seems that the discrimination went on more at local level. Stormont itself somewhat less so. But of course devolution was disbanded and direct rule from Westminster was imposed. By the mid to late 20thC, apart from possibly west-central Scotland again at ground level rather than government level, such sectarianism was completely foreign to the vast bulk of folk in Great Britain. Britain was certainly complicit in not clamping down on certain practices in Northern Ireland - possibly through fear of not rocking a reasonably steady boat. However once it hit the headlines the British public would have been the natural allie to those not being treated fairly in Northern Ireland. So I think Keith's main thrust is that the IRA's campaign was actually counter productive and rather than bringing a better Northern Ireland - it actually prolonged the time until that could be attained. It turned the attention away from the core issues on to the actions of the terrorists themselves. I kind of agree with Keith on that. As to their motives. I'm sure some perhaps genuinely thought it was the only choice they had - and I am also pretty sure others would have had no truck with the British no matter what the government did.