Against Radical Xenophobia
ARX is a double entendre, meaning both against radical xenophobia and base. The original purpose of the group was to help "misfits" who had been ostracized and to create a new world where they could be free.
The purpose behind using the word xenophobia was correlated to the belief that to cast out anyone except pure blood Ancients was prejudice against those other groups and a form of othering.
While the group remains strong in their beliefs, this was somewhat of a feint for their real purpose of finding the Lords of Light and Shadow and restoring the Balance through various acts that made them universal criminals.