Slavery in Utopia is not a question of race, ethnicity, or belief. It is a question of moral behavior. Only criminals can become slaves, and the children of slaves are born free. The slavery that exists in Utopia does not, then, contain all of the moral repugnance we rightfully associate with slavery. The fact that slavery could be conceived of as existing even within a fictional, ideal society is a sign that ideal societies are products of their times, subject to the beliefs and prejudices of the world from which they spring.
Similarly, the description of hospital care is revealing of the state of medicine in the early sixteenth century. The idea that a very sick person would not want to go to a hospital seems unusual to a modern reader, but during a time when it might be said that the only thing more dangerous then being sick was getting treated by a doctor, it is understandable. The Utopian practice of not only allowing but even encouraging euthanasia seems at odds with religious doctrine of the time, which believed suicide was a sin that would send its perpetrator to hell. However, euthanasia was a topic touched upon and supported by Erasmus, and Thomas More was certainly aware of that fact.
The marriage practices of the Utopians are called absurd by Hythloday and More, and seem absurd to the reader. It is not entirely clear what should be made of these practices, as they exist in what is supposedly an ideal society. A number of possibilities seem viable. Perhaps the marriage rites are another indication of the fact that while Utopia is near perfect, it is not actually an ideal society. Perhaps the marriage rites are supposed to be taken seriously, as an actual rational proposal. Perhaps they are simply a joke, since Thomas More was known to be fond of jokes. The text gives very little clue. The issue of divorce is a more concrete matter, and similar to that of euthanasia. The Catholic Church frowned on divorce even in the case of adultery, but Erasmus believed divorce was acceptable and necessary in certain situations. That divorce is allowed in Utopia is another indication that Utopian society was a realization of Erasmus's Humanist beliefs and arguments.
Visible in the rules guarding against adultery, pre-marital sex, and those abolishing campaigning for office is the Utopian understanding that mankind's baser instincts of lust and greed will never disappear. Utopian laws, for this reason, are formulated so as to powerfully discourage the vices inherent in human nature. These laws demonstrate that Utopia is not a society full of ideal people. Rather, it is a society that is formulated so that the inherent faults of man are contained as stringently as humanly possible.