I do agree that during desperate economic times political extremism flourishes. The nineteen thirties in Germany is a perfect example.
However I don’t believe Catalonian separatism is extreme. Self determination is surely an understandable aim for a region who believe they have a separate identity. I have no idea if a majority do. Why then prevent it being tested?
If governments don’t trust the people they forfeit the moral right to rule. That’s a corner stone of democracy.