I was a high school kid living in NYC at the time. I used to watch Cavett on TV all the time. Here's what I remember:
1) this was relatively big news when it happened
2) newscasts covered it. Newspapers covered it.
3) Cavett spoke about it on his show the next day (as he mentions).
4) I saw footage from that show. Did that footage air on the news on the day Rodale died, or did Cavett show some footage the next day? I don't remember, but there clearly was footage of the guy sitting in the chair just before he died.
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So, many people "saw" the event, in the sense that they pieced it all together.
Even when Cavett talks about "the look on your face", that also happened. People might not have seen his face that day, but Cavett was somber the next night when he explained the previous day's events. Many people tuned in for that and I'm not surprised they "remember" it.
All this is well understood. As Wiki claims: Memory is never a literal recount of past experiences. Rather, it is dependent on the constructive processes present at the time of encoding that are subject to potential errors and distortions.