Liverpool and Manchester United are the best of enemies. Sunday's Premier League meeting will be served with concentrated hatred flowing through both sets of fans at Anfield and over a century of fiercely-fought-for pride at stake.
When it comes to elements of the most ardent supporters of these two teams, nothing is off-limits.
Manchester United fans have been known to mock the 1989 Hillsborough disaster that saw 96 Liverpool fans crushed to death. Liverpool fans have treated the 1958 Munich air disaster with the same deplorable lack of respect.
Often, one crime is used to justify the other. But on Sunday, with Liverpool playing at Anfield for the first time since a new report finally revealed the truth of what happened on the terraces of Hillsborough—23 years on—the football community is holding its breath and praying for decency to descend.
Said United manager Sir Alex Ferguson, per the Guardian:
It is going to be a very emotional day on Sunday and we will support them in every way we can.
As a club we are totally supportive of Liverpool in the situation they are in. We understand what those families must have felt when they got that report.
Ferguson condemned chants of "always the victim, never your fault," which reportedly rang out during United's home game against Wigan, and has been joined by many in the United community to call for fans to behave respectfully at Anfield and beyond.
Manchester United Supporters Trust urge fans not to sing offensive chants about Hillsborough at Liverpool menmedia.co.uk/manchestereven…— Manchester News MEN (@MENnewsdesk) September 20, 2012
The hope is that the minority—on both sides of the rivalry—will get the message. The majority have got it all along, but the majority don't make the headlines.
The biggest fear is that heightened emotions will spill over into abuse and violence. Police ejected 17 people from the stadium when Liverpool and United met at Anfield in January and will be ready to act swiftly if offensive chants break out from either group.
We'll get a sense very early on on how things will play out.
In tribute to those who lost their lives at Hillsborough, 96 balloons will be released into the air before lunchtime kick-off, with captains Steven Gerrard and Nemanja Vidic performing the ceremony (ESPNsoccernet).
Anything but a dignified audience from United's visiting support would be provocative in the extreme to Liverpool fans, who have suffered a gross injustice while mourning their dead all these years.
To the same token, Liverpool fans can set the tone by behaving with respect themselves. Maybe, just maybe, the findings of the Hillsborough report can usher in a new era for their rivalry.
What started with the building of the Manchester ship canal in 1894—a development that undermined Liverpool's shipping industry and led to mass unemployment and poverty in the area—is now a tale of two warring cities we see played out on the football field and, most noticeably, in the stands.
It might lack the glamor of El Clasico, but the Liverpool-Manchester United rivalry easily matches that of Barcelona and Real Madrid for passion, backstory and meaning in today's game.
In footballing terms, it's United who have emphatically ruled the north west since the Premier League era began in 1992—winning 12 titles to Liverpool's none and, with great relish, eclipsing their rivals' all-time record of 18 championships in the process.
But Sunday's clash is about far more than football. It's about two football tribes coming together and putting their differences aside for a cause far bigger than either of them.