Celtic and Rangers are due to play each other in the semi-finals of the Scottish League Cup at Hampden Park.
Anti-sectarian charity Nil by Mouth said many of the people taking part in sectarian violence claim to be atheist.
Campaign Director Dave Scott told Premier: "Quite often a lot of these people use religion as a hook to hate people.
"Many of them wouldn't be found inside a church or a place of worship, it's really a hook that people use to hate others."
The match is the first test of the Scottish Government's flagship legislation on sectarianism which aimed at cracking down on the violence between what's perceived to be Catholics and Protestants.
That made it illegal to sing some songs at games which are deemed offensive.
Referee Hugh Dallas was injured by a coin at 1999 Old Firm match
The Old Firm has been marred by violence in the past. In 2011 three players were sent off and the rival managers exchanged heated words on the touchline.
Just weeks later parcel bombs were sent to the then Celtic manager Neil Lennon. Two Rangers fans were jailed for the crime.
But Dave Scott added: "It's very important before this fixture that we don't pre-empt violence and encourage people to behave well.
"But history does paint a very depressing picture in terms of arrests and behaviour.
"So we're hoping that the cooling off period, where we've had several years without this fixture, will let people think about how they want to behave and bring the game into the 21st century."