You don’t need a majority support to cause mayhem. 2% radicals with weapons are enough.
Norse - it’s possible for people to settle their affairs politically without having to shoot their way out.
Resorting to violence before you have exhausted whatever political possibilities exist is generally immoral.
When there is no other choice, then fine - IF those 2% that you mention actually represent the region, and aren’t just imported fighters or unhomogenously-armed groups.
Otherwise you get really, really bad outcomes e.g. like the Bolsheviks, or ISIS. Or the Taliban.
If someone were to arm chosen groups of Scottish separatists, what on earth would be the good? The Scots in general have chosen to stay in the Union. Nobody and nothing is stopping them from leaving.
.