It was the first incident of its kind at the new Wembley and police confirmed 12 people were arrested.
But local lad O'Brien, 23, defended his fans, insisting: “No, they have the right to do that. They've been supporting us all through the season. They should celebrate as much as we do.
“It's a team thing and they're part of the team.
"They can run on the pitch in my eyes for all they want, they deserve to."