It's nothing personal, as in to call these men "scum" is pointless as it's the lack of communication skills and tolerance levels that is the problem. Can't blame the trigger happy guardia here, just the way in which they are trained.
They're just doing a job, and are told what to do themselves.... So do as you're told and don't fuck about.
There is no reason to attack without imminent danger, but luckily it didn't escalate into a full blown riot.
Travelled all over Spain, watched city/England and Malaga CF plenty of times and never had any problems with Police.