Announcing the FFA action on Friday, Gallop revealed that both clubs had received previous written warnings about the conduct of their fans and had been put on notice competition points could be deducted if problems persisted.
"Loss of points that have been won fairly on the pitch is a harsh penalty, but it's in equal measure to the enormous damage caused by the type of antisocial behaviour seen in Melbourne last Saturday," said Gallop.
"The troublemakers are hurting the club they claim to support. They need to understand that the consequences of their reckless conduct will be felt on the A-League competition table if trouble persists."
Gallop said that true fans would never dream of hurting their club.
"I have great sympathy for the overwhelming majority of fans who are sickened by the misconduct of a few, but it's time to make the consequences clear to everyone," he said.
"We want a safe, enjoyable and family-friendly environment in the A-League and we won't tolerate bad behaviour."
Gallop said the disciplinary action was based on an extensive briefing and detailed reports on the December 28 incidents compiled by Victoria police, stadium managers and FFA's security advisers.
- AAP