Just seen this from the Tel Aviv Derby where a fan ran on the pitch and attacked one of the players Player sent of for retaliating - Id have said it was self defence Turned out to be a dumb move from the ref as all hell broke lose at the sending off and they had to abandon the game http://www.bbc.co.uk/sport/0/football/29894003 of course it may have degenerated anyway but I do think sending the player off was very harsh
If a fan every comes on the pitch, whoever that person chooses to attack should be supported in squating them down like a fly with a quick hook.