No country likes itself to be split apart, especially when a relatively rich part of the country tries to separate. I don't know about Spanish law, but serious attempts to break up the country could be considered treason where I'm from. On the other hand the whole civil war they fought 90 years ago makes the point quite complicated to the Catalan people.
If California tried to leave the USA, the American government would do anything in their power to keep them from leaving. This is still quite different, as Spain isn't as loosely structured a government as the USA, but it's equally preposterous from a government point of view.
Happened because of the "Velvet Revolution" (https://en.wikipedia.org/wiki/Velvet_Revolution) which was yet again the people pushing the government to do something. I think when parent said "No country likes itself to be split apart" they refer to the current people in power (the government), not the people actually living in the nation. Otherwise all successful independence efforts can be considered "The country wanted to be split".
As the industrial heartland of Spain, a lot of non-Catalans live in Catalunya. They don't want to suddenly find themselves in a foreign country. That's not "the people in power" - that's ordinary people.
There's quite a lot of nationalism in Spanish politics; when Franco died, there was no proper national reconciliation. Catalunya suffered quite badly in the Civil War and afterwards, and there should have been something like the SA Truth and Reconciliation Commission. Instead, they restored the monarchy, which was, as you'd expect, nationalist.
Indeed. But some countries handle independence movements with more grace than others. It's perfectly legitimate for a region to ask for independence. If the host nation is graceful, and (for example) allows independence referendums, a civil war becomes much less likely.
The host nation always fights back; but passing ten-year imprisonment sentences on the leaders of the secessionists isn't very graceful. Sending paramilitaries to beat up prrotestors and voters isn't graceful at all. A little more "graceful" is to resort to dirty tricks; Alex Salmond, former leader of the Scottish Nationalist Party, was dragged into court on trumped-up sexual harrassment charges.
Spain supports separatist movements elsewhere though. They have no issues supporting western saharan independence, even if the separatist groups are engaged in armed conflict.
Imperialism against people with abominable ethics is still imperialism.
When the southern states used their democratic institutions to secede, and then the North invaded 'to preserve the union', that was imperialism. Waging an imperial war and then freeing the slaves of the conquered doesn't retroactively make your war a just, non-imperialist one. It just makes you an imperialist whose moral views on slavery are superior to those of the people whom you conquered. But you're still an imperialist.
Now, if the Yanks had actually engaged in a moral crusade to free the slaves, that'd be one thing--but they didn't. If you think they did, then I'm guessing your understanding of the civil war comes from your education by said Union, or from movies. If this is the case, read a history book (Battle Cry of Freedom is a good start) and you'll find it impossible to believe that the Union fought the war to free the slaves. That the "moral crusade" nonsense is still peddled throughout the United States is a simple matter of the winners writing the history books (and nobody wanting to be seen sympathizing with slavers).
And since I'm certain you'll follow up with that tired old canard about the South starting the war at Ft. Sumpter, I'll provide you with the relevant history in advance:
0) Abraham Lincoln wins the 1860 presidential election on November 8, 1860.
1) On November 10, the South Carolina General Assembly passed a resolution calling for the people of S.C. to elect a commission to determine whether the state should secede.
2) Convention delegates were democratically elected on December 6.
3) These duly elected delegates convened in Columbia on December 17th.
4) They voted unanimously for secession.
5) The South Carolina General Assembly declared their independence on December 24.
6) At this point, American troops occupy Fort Sumpter, which at this point is foreign soil.
6) On Jan 9, the US attempts to reinforce the fort. They are prevented from doing so when Confederate artillery fires on the resupply ship.
7) On Jan 31, 1861, Governor Pickens demands the surrender of Fort Sumpter.
8) Lincoln sends multiple ships, with hundreds of soldiers and sailors, to reinforce the fort.
9) On April 11, knowing Lincoln plans to reinforce the occupying force, the Rebs once again demand the surrender of the fort. The commanding officer refused (then tried to play for time by making up conditions, which were refused).
10) At this point, American troops have been occupying foreign soil for ~4 months, and are effectively signaling their intent to stay indefinitely.
11) On April 12, the Rebs start shelling the fort. They shell it for 34 hours, then the Americans surrender.
12) After their surrender, before the Americans took down their flag, the Confederates allowed them to honor the flag with a 100 gun salute. One of the Yanks' guns misfired, killing Edward Galloway--the only American soldier who died.
You should feel free to say "well they were slavers, so fuck them". That's perfectly valid! But facts is facts, and the Civil War was imperialism.
Neither the north nor the south can really be considered democratic institutions by modern standards - less than half of their population could vote at the time of the civil war (women's suffrage) - and far less than half in the south (millions of slaves). The country as a whole elected Lincoln, and the southern states (via their mostly-undemocratically-elected leaders) rejected that slightly-more-democratically-sourced outcome. The democratically-elected leader and his political party then brought more democracy to the entire country by emancipating the enslaved and subsequently gave them (the men, anyway) the right to vote. Whether or not that was their intention at the outset doesn't change the fact that the north brought more democracy, which the south hated, and continues to hate.
So much for those vaunted democratic institutions you claim to hold so dear.
This doesn't contradict anything I said, unless you're under the impression that broad suffrage is a free pass to invade and conquer any nation with less-broad suffrage.
The North had broader suffrage than the South. The North freed the slaves after the war, and gave Black men the right to vote. And the Civil War was still imperialism. Do you disagree?
If California tried to leave the USA, the American government would do anything in their power to keep them from leaving. This is still quite different, as Spain isn't as loosely structured a government as the USA, but it's equally preposterous from a government point of view.