This is no small issue, and Spain is responding accordingly. The message has to be clear: Spain isn't going to split and we aren't going to allow tribalists/nationalists to act freely.
They are using rubber bullets to disperse the crowds, that's not exactly a crime against humanity as some seem to suggest here.
Having lived in Spain for some time, I can say police there is awesome. That is, friendly and laid back. Once I was caught smoking marijuana in my apartment (the neighbors called the police because of the loud music) and they made a couple of jokes and left. Back in Norway, they'd be angry & taken me to the police station.