let’s just ignore how the pretext for this line was Data observing how, sometimes, terrorism is an effective vehicle for social and/or political change.
edit: just to be clear, this isn’t a criticism, just an observation about the glibness of the meme as compared to the seriousness context.
that was Data’s whole point. Then, just as Picard was about to dish out a bunch of huffy, self-righteous moral indignation, their conversation got cut off by an incoming message or some other rather convenient interruption. Trek was often bold in how it approached controversial sociopolitical subjects. And, sometimes, it scampered off without honestly addressing them.
this occasion was one of the latter.
edit: although, one could argue that, due to the fact that Data got his comment in before Picard was able to give a self-righteous counter-argument, the writers, in fact, were quite brave. The comment was so controversial, in fact, the episode was banned in several markets which refused to air this episode, and it still remains banned in some places to this day.
Due to political sensitivity, as Ireland was still in the midst of the Troubles when "The High Ground" aired in 1990, the reference to Irish unification and terrorism in the episode resulted in its removal from first-run in the United Kingdom. To date, some syndicating networks will not air the episode, and it was only in 2007 (fifteen years after its first run, nine years after the conflict ended in a peaceful manner) that it was broadcast on the BBC.
Scotland could never leave. Britain doesn't want to loose Scotland and Europe doesn't want to split up all the British kingdoms and have them join one by one.
Northern Ireland has a chance to leave the shithole that is brexit by joining Ireland, but does Ireland want that? You're gonna spark a fire if you do that. The politics and rebellions of the 80's are only dormant, the sentiment is far from gone.