I agree with the guy posting earlier about that maybe this discussion shouldn't be on here as very few people know anything about it, neutrals will say religious 'hatred' between the clubs is a pointless exercise as it has little to do with football, however a forum is for discussions so people can discuss whatever the **** they like.
Can I first point out that the fact there is a religious conflict between Protestants and Roman Catholics isn't necessarily to do with football, and that Glasgow is really the only place where this goes[went] on. There is very little religious tension between Rangers and Celtic any more however going back 30 or 40 years was when we saw the Mo Johnson incident and the IRA chants. What this discussion is basically about is sectarianism, google 'sectarianism in Glasgow' to really get the full picture of the goings on.
However there is very little sectarianism within football today there is still a very small percentage of Protestants who support Celtic and an even smaller percentage who support Rangers, really though I just think this is down to family loyalty as opposed to the sectarianism.
Although the Catholics are the more vocal of the two it is in fact Rangers who are[were] known to only sign Protestant players, hence why the signing of Mo Johnson (in the 80's I think) was such a controversial signing, they are also more violent and in fact commit 70% of all sectarianism offences in Glasgow [Protestants in general].
Personally I don't many fans from England can comment about this much, I mean it wasn't too long ago that racism was huge here, there is very little difference between hating somebody for a religion as their is for their race so that's why I think most things posted here are slightly hypocritical and have taken them with a pinch of salt. Hopefully this helps a few of you understand the differences between Celtic and Rangers a bit better, however personally I believe the clubs are used as scapegoats for the religious tension within Glasgow, Celtic and Rangers have a joint campaign running in which they are trying to rid all sectarianism from football let's just hope it works.