It's all tongue in cheek stuff IMO. Yes there are some idiots who take it too far but you have look at the fact that all footy fans do it. Where I work some of the lads that are next door to my department are all evertonians and when they were above us last season they took great pleasure in having a large printout of the league table and if there was a nick name for any of the other teams in the league it was used i.e. Manure, the barcodes Arseholenal and for Liverpool it was the very imaginative REDSHITE, to name just a few. I knew that this was all just tongue in cheek stuff and that is the way that you have to take it and give it, it's all just part of the rivalry amongst footy supporters and as such shouldn't really be taken too seriously IMO.
As for the KOP magazine this is a publication that I and many liverpool fans that i know enjoy 'cos it is a look at the footballing world in a lighter way and instead of the usual watching what they say approach so as not to offend other teams and supporters bull that has crept into footy these days. The castle greyskull term is nothing compared to some of the terms that have been fired the way of liverpool down the years so i'd just pick up your copy of the KOP and have a damn good laugh.