I can always appreciate the "urge" to beat a perp, but we know that officers of the law have to refrain from such activity, and follow the very law they swore to uphold. It appeared to me that the one cop was jabbing the man with his baton. It's difficult to tell from the angle and view, but it appeared that the man was subdued and under control, and therefore the jabs looked to be excessive force.
The soccer fans must have been angered at such a show of force, over a seemingly mild "crime". We can assume, I guess, that the man who was beaten by the cops (security?), was a supporter of the team whose fans came to his aid. I guess they look out for one another. Given the volatile nature of foreign soccer fans, that's a bad situation to find yourself outnumbered in. Better hightail it out of there, or call in backup.