The Kosovo logic has been celebrated in the EU the for last 10 years, and according to that logic the answer from Europe to the Catalonia referendum would have been: Recognize the independence of Catalonia and bomb Madrid.
No evidence given. In Kosovo, there was a civil war, with thousands of casualties and hundreds of thousands of refugees, and which Western countries stopped. This was followed by a decade of international administration and status negotiations. In 2008 the EU Council stressed that in view of the conflict of the 1990s and the extended period of international administration under Security Council Resolution 1244, Kosovo constituted a sui generis case. The International Court of Justice has stated that the declaration of independence of Kosovo did not violate international law.