Saturday's FA Cup semi-final with Wigan was marred by Millwall fans who turned on each other as fighting erupted in the stands midway through the second half of the game.
Police say 12 Millwall fans were arrested after the brawl, including six for affray, and Shittu has spoken of his disappointment that a special occasion was ruined by a small minority.
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"There has been plenty of positives coming out of Millwall, but the minority shouldn’t be doing things like that. What does it achieve?"
When told of the violence witnessed in the stands the 32-year-old was shocked: "No way. Oh my gosh. It’s not just the players who are representing Millwall, it’s the fans as well.
"Everyone has to behave. Those days are over now. They need to stop doing stuff like that.
"You should come to the game, be passionate about supporting your team and then go home. You don’t get anything out of fighting. They just have to stop this now."
The disgraceful events will come as a huge disappointment to Millwall who have been actively trying to improve the reputation of the football club in recent years.
The club's chief executive Andy Ambler called those involved a 'mindless minority' and said: "Anyone associated with our club found guilty of violent behaviour will be banned indefinitely from Millwall matches.
"Having worked so hard to show the positive side of our club, both on and off the field, we cannot allow the actions of a mindless minority to undermine that."