Didn't Millwall cause trouble at Hull in the FA Cup last season? I don't remember a lot happening by way of punishment over that. I know it's nothing like the same severity or scale of last night, but I wouldn't be surprised to see the FA pass up the chance to take a strangehold over this and hand out swift and brutal punishment. Ban every person found being part of the violence, have some closed door matches and bring hefty criminal charges for all the destruction and harm caused, including conspiracy charges in relation to public order offences.
Not even our matches with Swansea had particularly bad trouble last year, and we've hardly played them that often in recent memory. This sort of thing is supposed to be consigned to the past, even amongst the more infamous rivalries.