Sectarian chanting in Scotland?

Not sure what to make of this phone video. It comes with the claim that it features two senior Celtic players, whilst the crowd chants ‘Sinn Fein’ and ‘IRA’ between lines of ‘The Fields of Athenry’. Green shades of Gazza and Donald Findlay? As we cannot verify the claim and to circumvent any legal complications, I’m suspending the comments on this one.