Green Again, can you define "grief"?
Annoyance because the person sitting next to you has a different affiliation to you? Why does it matter? Literally every other sport this isn't an issue.
Lose the tribal mindset and grow up.
That's not the point though is it. The fact that some people will kick off means there is a greater chance of trouble in the stands, where there might be kids nearby.
Until they allow mixed seating then the fans need to be segregated.