Demetriou said while he believed Saturday's incident, which saw Brad Jones seriously injured after an altercation with Collingwood supporters while leaving the MCG, to be isolated, the AFL would not hesitate in prohibiting offenders from matches.
He also said clubs would support the league's anti-violence stance and revoke memberships of anyone found to misbehave in a violent way at games.
"Let me be clear about this; the AFL, our clubs and our code is a game built on families attending," he said on Monday.
"We will not tolerate anyone coming to our games who seeks to inflict violence on anybody, whether it's during the game or after the game.
"There is absolutely no place for that sort of incident in our game. We will work with our clubs and supporters and venues to make sure anyone who thinks they can engage in that sort of activity ... we will fine them, identify them, and they will not be allowed to attend our games.
"The police acted very swiftly after the game with this incident and we congratulate them for doing that, but at the end of the day, this is a truly horrible incident and one which, I repeat, has absolutely no place in our game."
Demetriou said the league was confident it could police bans handed down to anyone denied entry into grounds.
"It won't be easy, but I can assure you we will use every method and work with groups who specialise in this area to make sure that entry points at games will quickly identify someone who has been involved in an incident like ... on Saturday," he said.
"At the end of the day, we invite people to come to games, to come in comfort and safety, to be part of a group of people who watch the game as inclusive as possible, and have no fear of attending these games.
"If there are people out there who think they are going to use the vehicle of AFL football to come and express their anger in violent means, they will not be welcome."
The warning comes the same day the SANFL banned an Adelaide Crows supporter from AAMI Stadium for the rest of the season for throwing a drink bottle during Friday night's clash with St Kilda.
The bottle was aimed at the umpires officiating the match, but hit a child instead.
Earlier on Monday, Collingwood midfielder Dane Swan said clubs and players expected fans be able to attend games without the threat of violence either during or after the match.
"I think there is no question that everyone wants their fans to behave at the football," he said, at Collingwood's recovery session at the St Kilda Sea Baths.
"The MCG and all football grounds should be a safe place for their families and for people to go and watch footy."
Demetriou said he had spoken to Nathan Jones and expressed his "extreme disgust" over the weekend's events to the Demons' midfielder.
"Everyone involved in football wishes Nathan's father the speediest of recoveries," he said.
"When I spoke to Nathan, I also asked after his younger brother, understanding full well it would have been very traumatic for a 13-year-old boy to be witnessing the incident.
"There is absolutely no place for that sort of behaviour at our game."
