But was it actually controversial or was it greeted with indifference? I suspect this might be another case of print the myth.
When "Plato's Stepchildren" first aired, I think Star Trek
was on at 10 pm on Friday night. That's a graveyard shift for TV because the desired demographic goes out to movies, parties, bars, etc. Children were in bed and that left older folks, many of whom were already asleep as well.
That, plus the blink-and-you-missed-it kiss duration, and the fact that many viewers who did tune in probably considered it a deeply lousy episode and didn't stick with it that far into the timeslot, and I would bet that The Kiss didn't cause any stir at all in 1968. The nation was reeling from actual events and would hardly be on pins and needles to see what went down on Star Trek --
in a silly, frequently embarrassing episode, no less.
Even today, I notice that none of the shows I give a damn about are shown on Friday night.