I don't get this 'don't fight each other' thing.
I don't know 99.99% of the people there, and they will get a slap if I think they deserve one. Couldnt care less if they support Saints or not.
Likewise, If I annoyed someone else, I would expect a slap.
During the rest of the week, I don't ask everyone who they support before getting into an argument with them.