All art is inherently propaganda on some level as every work by every artist seeks to convey and persuade the audience to at the very least see the point of view of the artist, if not embrace it, no matter how mundane the subject.
well put, propaganda though has negative connotations which is why i think someone already objected to it, however it is accurate. any person who views, hears, or reads your works is an attempt to influence them to your vision. other wise art would be pointless. television shows are no different, ignoring star trek for the moment, writers hope that you'll either identify, like or be interested in the story or character(s) and many if not all include moral quandaries...since drama makes things more interesting, especially when happening to other people.
TOS, and the other series were a mix of moral choices, filler, and commentary on society, it's values or lack thereof. so propaganda. anything that attempts to influence your way of thinking/acting is propaganda...that doesn't make it bad. trying to point out that murdering people = bad is a good thing, that tolerance is better than hatred, that choices have consequences beyond just yourself, etc.
though, trek franchise as propaganda is actually extremely accurate...it's created it's own cult >trekkies/trekkers.
Sadly, there are some who have become so jaded as to consider any form of communication or teaching to be a negative thing, some attempt to 'make' them think something, and thus they reject it or dismiss it as 'propaganda.'
Only listening to yourself or to yourself and to those who agree with you is the easy route but leads only to stagnation of ideas.
It is important to listen to others, and think about what they say even if it might not make sense to you at the time. Even if their ideas are bad ones. Just as no one is completely infallible, no one is completely incompetent either.
Neither agree nor disagree blindly or without thought, but keep an open mind.
Star Trek was (and is) a commercial product but it has also been a medium for exploring ideas and ideals. Thankfully something can be both and be useful in both capacities
TV shows are made by real people and everybody has their own view point, religion, agenda or what ever you want to call it. these viewpoints will seep into the shows they produce to different degrees. sometimes intentional and sometimes unintentional.
if making people think about the real world issues through a sci-fi story (ie racism, slavery, war etc etc) or trying to convey the producers hopes for humanities direction is propoganda then yes, it is. Its not a negative propganda but there are certainly views within star trek that are deliberately being created by the writers.