At least it's relatively minor disorder but away fans have to be kept back for high profile games. Really that was the first high profile game fan wise. Man United on a Monday night in winter, in a tame match, didn't really cause bother, same with Leeds. But a weekend game in April with the sun out, and a lively affair against the biggest rivals, you can't just have a hands off approach when there's so little segregation.
Coming out of Goodison for a wild derby last season, I thought then it would be chaos at the new ground if away fans weren't held back. It might have even been worse had they not scored at the end because that caused a mass exodus from the home ends while they stayed behind celebrating for a bit, rather than everyone getting off at full time after a draw.