Like so many things, what starts as being a movement that brings economic growth and prosperity to a resort/area/country, over the years grows so large that the conomic advantages begin to fail as the very things that made somewhere popular begin to degrade it.
So many areas that drew tourists in because of the beautiful beaches/ wonderful architecture, peace and quiet now have so many tourists that the beaches are full, so much housing has become holiday accommodation that the locals cannot find homes, streets are heaving masses of people. I am not surprised that the people in many tourist areas of Spain are fed up.
50 years ago I fell in love with Oxford, I wanted to live there, couldn't afford it, but for the last 30 years have lived 10 miles away. I used to go there a lot, parking was easy, if expensive, you could walk round the colleges and their quads, and no one would stop you. In the vacations they were quiet and peaceful. The town was full of indpendent shops.
Now, you cannot move in the city because the pavements are blocked by tourist parties, the shops have all closed to be replced by chain restaurants. The colleges only let people in to visit at certain times and charge a fee, I do not blame them. I now rarely go to Oxford, all I loved has gone, it is just a tourist destination full of eateries and booths selling tawdry souvenirs.
My sympathies are all with the protesters of Barcelona.