Troubling Utopia

This evening, I tutored a student who has been doing a group assignment on "designing Utopias" for her high school class. I mentioned that I had also been touching upon this very same subject in the Gulliver's Travels Grade 4 class that I am teaching, specifically since the topic of Utopia had been quite "hot" in Swift's time. What was interesting was the discussion that ensued between us, which ranged from the nature of government (democracy vs. meritocracy), how Utopia would be "policed" (in this case, robots were one possibility), and how crime is controlled (alas, the group had resorted to an "atomizer" which disintegrates unwanted things and reconverts them into new things).
    I have encountered the topic "design your own Utopia" in many contexts up to this point, all of which proved to be somewhat wild experiences. My first encounter of it was in seventh grade, in which I had been asked to design my own "planet", while my second encounter happened in the context of reading Golding's Lord of the Flies in eleventh grade. Finally, teaching Utopias has been another interesting foray. I personally can't quite pin a reason for this topic: is it a chance for young people to discover the kinds of societies they would like to live in? A way to think and reason sociologically?  Or is it an exercise in pure imagination? More than anything, Utopias reveal one's own personal yearnings, especially at the age where one hasn't quite found their bearings yet, and there are so many possibilities opening up.
   At times, I don't quite know how to teach the unit on Utopias. Today, the student talked about how her group discussed their ideal Utopia as having "only one race"and "one civilization which includes all others."  In addition, there was even some discussion regarding outcasting elders who reached a certain age: a point which was later replaced by the somewhat more humdrum option of uploading one's memories into a supercomputer after one's body has reached a certain old age. Whereas the second point raises issues about aging, the second relates to how diversity is approached in Utopia.
   I think the idea of  having a single "race" of people way to resolve the challenges of diversity, but it raises so many problems. Whose race, more specifically, will represent all people in Utopia? In addition, I wonder how I as a teacher am to respond to this idea, given that it has very terrible historical precedents such as genocide. Do I simply entertain this idea as "possibility", or might I challenge the student to find ways to honor diversity or re-think about inclusion in the world they are envisioning? I tend to go with the latter, albeit carefully, because the exercise is an opportunity to raise questions as well as link imagined worlds to actual worlds in which humans have been historically situated. Just as Swift used various "ideal" worlds to shed light on the world of 17th-18th century England, so it's also conceivable that one's Utopias can lead to very sinister ideas that actually need to be brought out to see their full effect and to challenge them. At the same time, however, I have to be careful to allow the students to give free reign to their imagination and for the ideas that they are raising to come up from their own hearts. My attitude has been to try to listen to the students to understand the ways in which they are coming to their own conclusions regarding how societies can address issues and run properly.