A 'sitist' is a person or
entity (
corporation, website etc) that discriminates against websites supporting such a person or
entity, based on unfounded assumptions.
Jagex (the makers of the
MMORPG, Runescape) doesn't recognise Zybez.
net as a fansite for unfounded reasons (apparently there are
bad advertisements on Zybez, which don't actually exist), therefore Jagex are examples of siteism, referred to as a sitist.