I don’t speak French. This video shows a guy running across a soccer pitch with a sign. He is tackled by some cops, and one of them is seen plunging his baton into the guy. A soccer player runs over to break it up, and then the fans joined in.
Who, (I see what), When, Where, and Why?
For all we know, neither does the announcer – he’s speaking Portuguese in this clip. 
Apparently:
Who? Benfica (Lisbon, Portugal) vs Étoile Carouge (Switzerland) in a “friendly” game, + relative of referee + Protectas private security guards + crowd.
When? July 17, 2004.
Where? La Fontenette stadium, near Geneva, Switzerland, home of Étoile Carouge.
Why? From here (which matches info at other sites but sums it up better):“The initial protester thought the game had ended (it was in fact in extra time), and was expressing his support for a relative, the referee of the game, a Portuguese migrant in Switzerland. The security guy who gets knocked out is also Portuguese, as most of the spectators. He ends up walking away on his own, after being unconscious for a few minutes. It’s all good and no one was arrested.”
Further info here, claiming that 3 security guards needed to make a trip to the hospital.
Benfica (the Portuguese team) won 2-0.
Further confirmation: here is an archived article (in French) relating the incident.
The first half of the article describes the incident, the second half gives a synopsis of the match.
I had the sound kind of low. The friend who sent it to me said it was Portuguese.
Thanks for the info.