"...his knowledge of child sex allegations against [his] brother – allegations which Gerry Adams claims to have believed from ‘the very beginning’ - for over twenty years without having brought them to the attention of any authority North or South...".. then it's hard to see how even a low-level politician would survive such a revelation - never mind the President of a political party.
On a lighter (!) note, it raises a point for me about the way that a rejection of civil society on political grounds - i.e. 'we won't co-operate with the police in any way because we reject the flavour of government that the policing is grounded in' - highlights the fundamental problem with the IRA rejectionism: That it is unable to reject the social contract in part.
In practical terms, you either take the rule of law or leave it. There isn't a practical way of going halfway. When Irish Republicans chose to leave it, they ended up countenancing something far worse than British rule. They countenanced a pragmatic alliance with drug-runners, protection racketeers and local vigilantism in all of it's nasty glory. Their political actions carried disproportionate levels of violence, they covered up their own 'accidents' and left bereft families without answers. It created a fractured society - and one, ironically, that no 26 county government would ever wish to absorb.
If these allegations are true, Gerry Adams chose to leave a known child abuser to his business. There is a warped sensibility in Irish Republicanism that may understand that action in the context of an inability to involve the RUC. To promote the same brother as a potential elected representative, however, must surely be unforgivable for even the most stubborn Republican.