If Spain really wanted to quiet down the independence movement in Catalonia, they could actually introduce a democratic, non malapportioned voting system. Americans would be proud of the Spanish non-democratic electorates.
The Spanish have basically gone off and said "how can we make an on-paper proportional voting system repeatedly return majorities for the minority who we hate and who are destroying our country". The problem is, as always, that no politician would ever vote themself out of power, and so no-one in Spain will ever propose a democratic reapportionment.
The real issue here is not about the identity of the Catalonian people, it's about money. The catalan politicians have instigated nationalism but real issue is money, as in "why we catalans should contribute this much to the other regions of Spain that don't produce as much?"
It's turtles all the way down.