Like the Islamic terrorists, they only get as far as they do thanks to the discreet compliance or looking the other way of the associate group.

It'll be interesting to see if a rift forms between the native Irish population and The IRA/Shin Fein. For the life of me I can't remember a militant group losing the support of it's associate population but I imagine it would lead to less safe places to hide or store weapon cashes, even the forming of breakaway groups actively antagonistic towards the main group.