So you think any political entity, regardless of where it is located and how it is incorporated into a larger entity should just have a carte blanche right to secede or separate ?

No. I think that there are a lot of reasons why secession is either a stupid or absurd proposition. If secession would, for example, create a state dependent on the larger entity for food, energy, military, education, health care, etc., the notion is preposterous.

Catalonia, Texas, and California are all perfectly capable of operating as independent entities. So, in those cases, I think that a nation that claims to be “democratic”, but would not permit secession, has a rather jaded view of what “democracy is.”

And why only a “supermajority” ? Why not just a majority? or why not 3/5ths?

Because it’s not something that gets walked back easily.

Where do you draw the line? Should Bavaria now get to separate from Germany? Provence from France?

I don’t know the condition of either of those states, so I can’t comment. Apply the metric from above.

As I noted in the original question, Spain has been a geographically/politically cohesive nation since 1492. This is not an example of Yugoslavia cobbled together in the last 70 years or various middle east nations whose lines were drawn arbitrarily by western powers 100 years ago.

True, but there is a language issue and a unique culture in Catalonia, as well as having it’s own economic engine and would include one of the world’s most significant cities.

Free markets, free minds. Question all narratives. If you think one political party is right and the other party is evil, the problem with our politics is you.