The link is to an article about seven agents of the Spanish National Police who started a fight in a bar in Barcelona yesterday. Off-duty and drunk, they mistook the Italian waiters for Catalans (not knowing even vaguely the difference in the difference in how the two languages sound) and demanded that they speak Spanish (among themselves) because "Barcelona is Spain!".
This kind of thing doesn't happen every day, but if you live here, you're not surprised when it does. There was recently an incident at the Barcelona airport when a traveler was speaking Catalan and a Spanish police agent arrested him for not speaking Spanish.
The Spanish Guardia Civil and Police National are typically antagonistic with Catalans and the Catalan language, which they, for the most part and in spite of some of them being stationed here for their whole career, don't speak. When I first came to live in Barcelona and was being bothered and followed by a beggar on the street, I went up to two National Police to ask for help, speaking in Catalan. They made like they didn't understand what I was saying. I realized afterwards that if I had spoken in English, they would have figured it out. Thinking I was a tourist, help would have come. Thinking I was a Catalan, they couldn't care less, even though it was their job to do something.
That experience colored my perception early on as to how to view and behave with the Spanish police forces. It's a little like blacks in America, an experience I also had when I was visiting in Los Angeles with my black boyfriend and we were arrested for driving in a car with stolen license plates even though the car was mine and I produced the car registration. But that's a long story. Just to say that blacks in America don't trust police for good reason, and here I feel the same with the Spanish police.