There are perhaps as many reasons to loathe this episode as like it. Reasons to loathe first:
- Guest aliens forcing our characters to do silly things.
- The overly-familiar template of guest aliens having a society our characters need to set straight.
- The overly-familiar template of guest aliens just happening to have patterned their society after something in Earth's past.
- Plato not even particularly being well-represented, so really, what was the point of using him at all?
All that being said, there's at least one great reason to watch "Plato's Stepchildren," and it looks like this:
That would be Uhura kissing Kirk, the first interracial kiss seen on television (the Memory Alpha link provides some clarification, but the point stands), an historic event for which this episode, and indeed the whole series, will forever be known. Sucks that it has to be under the auspices of alien control and all that, but there it is. It happened. Glad Star Trek made history like that.
That alone makes the episode must-see for its cultural significance, but there are other reasons, too. There are franchise-specific reasons, parallels to be accounted for, trends to follow (eugenics, as in Khan; emotional transference, as in Lwaxana Troi in Deep Space Nine's "Fascination").
There's also the plight of Alexander, which becomes the crux of the story. Alexander is one of the guest aliens, only he's considered inferior to the others. Our characters end up spending their time not so much fixing the society as fighting for Alexander's rights. If you like, this might be considered another level of the general Civil Rights push of the episode along with the kiss.
The good, in the case of this episode, easily outweighs the bad. A real argument could be made for "Plato's Stepchildren" representing not only the third season but the series as a whole, the reason why something that seemed doomed to be lost and forgotten instead became a global phenomenon.
That's easy to call a classic in my estimation.
four quarter analysis
franchise * series * essential * character