Does "The Ones Who Walk Away from Omelas" pose a challenge to cultural relativism?

It's an interesting question because at its core, "The Ones Who Walk Away from Omelas" is a thought experiment which poses a moral question. The interesting thing to consider, however, is that ultimately, the quandary represented by Omelas has real-world implications when you consider that problems of suffering and exploitation are very much ingrained in civilization and in the human condition.
In this work, LeGuin is ultimately asking the question of how one comes to terms with this problem and with our own collective complicity within it. In "The Ones Who Walk Away from Omelas," she imagines an ideal, utopian community—and she's quite clear that the particularities of that utopia do not matter, for this is only a thought experiment. At the same time, she notes that the collective happiness of the community is founded upon the suffering of a single innocent child, brutalized and tormented in horrific fashion. The question becomes: how does one respond? Most people stay within the system, but there are a few who cannot accept this contract with suffering and choose to leave the community (leave paradise) rather than be complicit in the cruelty which forms the foundation of that system. What happens to them is unknown.
So now the question becomes this: how do we apply this to a subject like Cultural Relativism? And there your question becomes interesting, because again, ultimately to look at Omelas seriously means to be conscious of the full scale by which abuses and suffering is endemic within the human condition (Omelas can well stand for a symbol of human civilization), and this would stretch across all cultural lines. From one perspective, it does seem to uphold one of the critical tenants of cultural relativism—that we should not judge foreign cultures by the standards of our own or assume our own values are superior to those held by others. The message of Omelas is that we all have skeletons and are all complicit. However, at the same time, LeGuin's story does imply a deeper moral absolutism, by which all societies can be judged according to the suffering they inflict and how they themselves respond to that suffering.
If we are all Omelas, that has very real implications about how we address the problem of suffering and its prominence within the human condition.