This is the term I decided upon for my upcoming novel, Red Noon At Helltowne, to reflect the tyrannical attempts at Forced Equality that has and will continue to do so much harm in the land of the Shenbyrg Vale. Unlike 'Egalitarianism', 'Equalitarianism' is more obscure and also holds its root 'Equal' more obviously. This not only fits well with the novel's style of using more obscure words to reflect its fantasy future setting, but also the overall theme that even though some tyrants may claim that their goal is Equality, it is often really only an excuse to diminish certain other groups that they don't like, ironically creating even worse inequality. Think Animal Farm.
In the case of Red Noon At Helltowne, the red dwarves are using the goblins (as well as another terrible weapon revealed at the end of the book) to try to annihilate Dinglesfuhr. A particularly warped Cult has assumed power there, which espouses the cause of Underreign in order to promote Equalitarianism. Will it be any wonder that so much of the awfulness of Helltowne could become recreated in Dinglesfuhr? Perhaps even the insane cultists won't be that surprised?