Hmm, maybe if you want to know what the people of Cataluña want, maybe we should ask them? Perhaps by holding a referendum to get their views on the matter?
(Note that a similar situation in Scotland was addressed by doing exactly this. The referendum was done begrudgingly, and certainly was not popular in Westminster, but it did happen, as it should have -- even though I'm personally glad they voted to remain.)
Question: Do you want Catalonia to be an independent state in the form of a republic?
That premise does not necessarily lead to that conclusion. Ask the USSR.
Playing devil’s advocate. Referenda may prematurely compress a multidimensional discussion space into binary options. There’s no “I’d prefer to stay in Spain if X, Y and Z.”