I believe that Catalonia should and have a right to become independent from Spain. As for now, Spain's government does not respect this right and tries everything in their power to prove that independence referendum was not legal, etc. in this way disregarding Catalan people who have voted in this referendum and expressed that they want their own country. If Spain is modern and has any democratic values, it should let Catalan people decide and respect any decision that they make.
This is the age of integration, not disentigration. Nations should not be falling apart due to petty minor cultural differences. The Catalans are spanish, with only small differences. However, they are determined to be independent.
While there should definetly be the right for Catalonia to have a referendum about being independent, they shouldn't really.