So when did we break international law wrt to Scotland? In modern times. Did we do any of the things you mentioned? Did we persecute them?"Crushing" any attempt? Last I checked Catalans weren't second class citizens aren't actually enjoy some of the best living conditions in the entire country.
As usual context is key. Any coup d'etat or illegal declaration of independence requires very extraordinary circumstances for someone to sympathise with the breaking of the law. It requires the state to be breaking international law in my mind which Spain has never done to the people of Catalonia. They have not engaged in ethnic cleansing, persecution of culture, religion or treating the citizens any less than an in the rest of Spain.
To even compare it to the historic examples of unilateral declarations of independence where the situation is far far worse is a betrayal of what those states went through and why they resorted to it.
And yet they still have a large indy movement and we were prepared to let them vote on it. And we will let them vote on it again, should they wish, at some point in the future.
The question is, is it ethical impose your rule on a sizeable group of people - whoever they might be - that do not wish it. Is it ethical to force a large section of your country to remain part of something they wish to leave. Is this always a case of majority rule, where the majority can/should be able to force the minority to stay/comply?
And would we be praising Putin if some part of Russia wanted to secede, and he used threats/riot police/force to stop it? Is this a case of might makes right?