Me personally, I have to wonder. If you don't recognize blanent messages of racism in a TV show, would you recognize them in real life or be just as oblivious?
Remember that in 1968, cities were on fire because of racial tension. Rather than take such a volatile subject on directly, Star Trek addressed it indirectly. It only works if people recognize the connection, of course. Those who didn't recognize the negative results of discrimination in 1969 had to be living with their heads buried in the sand. You didn't need a TV show to illustrate it; the Nightly News did an excellent job.
I think you're missing our point.
As *individuals*, both exodus
and I found the episode preachy and obvious, not worth the lauds you're giving it. But, as an individual, I was already well aware in 1968 of how heinous discrimination was.
And yes, shockingly enough that's from personal experience. The day after Dr. King was shot, my school bus was stuck in the midst of a riot--imagine 22 elementary school kids down on the floor of the bus doing a "duck and cover" while the windows are shattering over their heads. And at night, my dad was out in the hood as a reporter, driving with Jackie Robinson who was in town for an event, and was trying to keep the peace.
So for me, the episode was--even on first viewing--not all that remarkable. And I daresay that when you watch it today, it comes off as dated and... yes, preachy.