It's all down to pretending that you are irish. And that is what Celtic fans do best. Likewise, many Rangers fans will support the crown and thus England. Unless they happen to be in the company of an Englishman that is, then it becomes okay to hate them

Some very broad & inaccurate stereotyping there Mikky.
of those old firm fans in glasgow the stereotype is 95% accurate outside glasgow it is inaccurate
Yes both statements are true.
While we're at it 95% of scousers have bubble perms, moustaches, wear shellsuits are unemployed & would steal your car stereo &/or hubcaps before you could say "arr ay calm down calm down". They also possess a good sense of humour.
OK, I made the GSOH bit up.