I translated the text on that page, this is the reason why the Police attacked:

The Autonomous been forcibly evicted camping Movement 15-M in the Plaza de Catalunya in Barcelona. With public health reasons, and facing a possible conclusion of FC Barcelona, ​​the police have finally charged the protesters to try to disperse and make way for municipal cleansing vehicles (ATLAS)

To make way for the trash collection and street cleaners? F*ck that.