'The ones who walk away from Omelas'

On 31th June we travelled out to a park, sat under the shade of a tree and discussed 'The ones who walk away from Omelas' - Ursula K. Le Guin. I cannot recommend this reading enough. It takes a while to process, but what I learned from it was that we can easily speak of how would do the right thing in certain situations, but once we realise the situation is actually what we are living in right now, we find it difficult, if not impossible, to change. Especially when that change causes us hardship.
After the reading, we were asked to place ourselves in the city of Omelas and discuss what we would do. The jist of the story is that the citizens of Omelas are blissfully happy with no hardship whatsoever. But there is one child who lives locked in a cupboard on its own excrement and is miserable. The happy citizens of Omelas have never experienced hardship or sacrifice, they have not earned their eternal happiness. If the child were ever to be freed, the remaining citizens would no longer be blissfully happy. The child is sacrificing his happiness so everyone else can live in permanent blissfulness.
I believe that there cannot be happiness without sacrifice. Would one want someone else to sacrifice for one's own happiness? Usually the answer is no, and people are disgusted to hear about this child. Yet when we draw parallels with our world, we realise that we are happy, yet most of us do not experience sacrifice. The poor beggar on the street is the child, the undernourished in the third-world are also the child. We see their hardship, but how many of us walk past beggars in London's city streets and pretend them not to be there?
It is easy to say that we would do the right thing if we were in the story. Yet we are in a similar story and many of us are doing nothing.