It's talking about the location of the inappropriate behaviour. The 'pitch' is the field where the football match was played. It's a very common term in British English, e.g. football pitch', 'rugby pitch, 'cricket pitch' etc. or often people just say 'pitch; by itself. i believe in American English they would say 'field' instead.

Thanks alot

The pitch is the field, or surface, on which the game is played. "On the pitch" can be taken literally as "on the field" or "on the playing surface" or it can be taken to mean "during the game". "There was more violence on the pitch than on the terraces" could be taken either way. I think in this case "during a game" is the closest equivalent.