Glasgow Celtic FC: Football/Soccer team supported by mainly Scottish catholics (with or without irish decent, although commonly with) and every plastic paddy around the globe. Fans of this team often sing pro IRA songs. Now Pro- Irish Republican Songs are not really offensive to most like minded Rangers fans and indeed non rangers/celtic fans in scotland, however, pro -IRA/terrorist stuff is!!!!
Glasgow Celtic FC: founded by an irish monk in glasgow to help support poor irish immigrants in 1888.
GCFC: claim to be a scottish side however youd be hard pushed to find any of their fans flying the blue and white saltire at their stadium (the scottish flag for those of you who are thick or just american) instead it is a sea of tricolours (rep of ireland flags) and other irish flags. It's particuarly strange and I suppose sad that a sizeable portion of these guys have little or no irish blood in them, being scottish catholics of scottish blood. Ok most catholics in scotland now are of irish decent but it wasnt always that way. (see definitions of Scotland
by bigmanofscotland for more info on this)
What it is I am saying is that it is ok to fly the odd irish flag if u happen to be one of those paddies who get the ferry over for the celtic games every weekend to keep the "culture" or "heritage" of the club alive but for gods sake not if ur anyone else. However if u do then ur just the same as the rest of the worlds plastic paddies: like the ones in the US for example who go to see celtic play when their in town because its an IRISH thing to do. So thats why GCFC is not a scottish team and thus why they are disliked and found irritating at the least.
PS. thankyou NEW ENGLAND REVS for inventing the great chant "where in ireland is glasgow" = GENIUS, spot on and well done. thats all i can say.