I'm an English Celtic fan. I can understand other fans in Scotland hating Celtic as we are the most successful and widely supported Scottish team, the same way most fans in England hate Man United and most fans in Germany hate Bayern Munich etc. However I've always wondered why so many English fans hate Celtic so much.
Most of them do so because they say Celtic fans support the IRA. This is true, but I don't really see a problem with supporting an organisation which fought for Irish independence from Britain. There are no songs sung by Celtic fans on a matchday which glorify or even mention the PIRA.
Celtic fans do not engage in any sectarian singing; there are no songs sung by Celtic fans which carry slurs against Protestants. The same, however, can't be said about the fans of deidco, formerly known as R*ngers (RIP) who openly sing sectarian songs about Catholics. Yet these fans and that club, for some reason, are much adored by a lot of English supporters. There is so much more that could be said about our dearly departed neighbours, but I'll try and stay on topic.
We also seemed to be hated for our refusal to wear the poppy. In a match vs Aberdeen the Green Brigade ultras group held up banners which read 'Your deeds would shame all the devils in hell. Ireland Iraq Afghanistan. No bloodstained poppy on our hoops'. This was met with complete outrage at the time. Many Scottish Celtic fans originate from Ireland and indeed many Irish fans are season ticket holders at Celtic Park and take the ferry from Ireland for every game. So why does anyone expect them to welcome a symbol of the British army, who occupied and oppressed Ireland and the Irish people for centuries, at Celtic Park and on the Celtic jersey? If one was to give an American flag to an Iraqi boy, who's country has been invaded and destroyed by Americans, he wouldn't exactly embrace the flag. So what's the difference here? The resistance to wearing the poppy by the Celtic support is completely justified imo.
So why do so many people hate Celtic? To me it seems like the cool thing to do. Many people don't even bother looking at the history of Celtic and the history of Ireland and just jump on the bandwagon of hating Celtic and liking R*ngers, because it seems like the norm amongst English fans when it comes to the Old Firm.