Booing your own country is just ridiculous. Even if you’re staunchly regionalist and separatist I just can’t stand the fact that people would boo their own country. Athletic Bilbao fans are notably quite separatist and want the Greater Basque Country to separate from France and Spain to form a Basque nation (similarly many Barça fans want Catalonia to become independent).
In terms of what I think of these movements, I support them when the people do or when practical and with a purpose. A stateless people having a state, e.g. Assyrians or Kurds, yes. A gradual approach to decolonisation like the French Pacific, yes (even though I would agree more with the loyalist side on everything else). Just randomly creating countries, no.
The autonomous regions of Spain and the countries of the UK for example need unification in my opinion, but of course it’s up to the people to decide. Polling shows that people don’t want independence from Spain (though Scotland is on a knife’s edge). Referendums would probably be a good solution though.