South of the Pyrenees is Spain. The union was fought for with Spanish blood. The Islamists once tried to take it. Spain recovered their Nation. They must stand together with other Nations in the West to survive the challenge again.
That sounds very much like Falangist propaganda to me Ptr. You seem to have forgotten Portugal also inhabits the Iberian Peninsular.
No nation is set in stone. Countries evolve democratically. Governments have to respond to a majority choice or face conflict.
The UK has been one nation since the Union of Crowns in 1634 but that does not mean Scotland or Wales cannot have a vote of choice for independence.
History is littered with smaller countries gaining independence. France only became one nation relatively recently.
An independence referendum is only a political process and a desire for self determinism and cultural expression.
Your’s and the Spanish government’s belief is to to deny the Catalans even that.