The idea of Mr. Rogers cheerfully flipping the bird to children, and a double flip too, seems unthinkable. And yet here he is doing just that.
By every account I have read, Fred Rogers was as gentle, kind, and good-humored in real life as he was portrayed on his eponymous show so of course there is a innocent explanation for this. Jason Weisberger tells us that Mr. Rogers was singing a song with children in which each finger had a name and was raised as it did something in the song. The middle finger was ‘tall man’.
I was wondering if Mr. Rogers was laughing so much because he knew how incongruous it was for him to make the gesture and it is also possible that the TV crew, also enjoying the joke, made sure that he was in close-up when he did it.