It's now becoming apparent that some people have a seriously negative "trigger" regarding any video that's taken vertically. In addition, they assume their reaction is the only normal one, and expect every other person to have the same reaction. That is why they can't understand why others don't see the same humor they do in this video.
Just to make a stab in the dark guess as to the discrepancy in people's viewpoints here:
HA! Yes. You’re getting close.
As the father of a millennial (who just graduated today with a BS in Biomedical Science), it’s a running argument I have with her and those of her generation. In fact, I had to argue with my niece to take our photo horizontally today!
You rightly point out the most common form factor that Millennials view photos and video is a phone in portrait (vertical) mode. Thus they’ve been conditioned to capture images vertically.
For those of us who have been taking photos for more than 10 years, it’s crazy annoying to see vertical photos that aren’t portraits or fashion shots. Video in portrait mode drives me bonkers!
So yes, it’s a generational thing. But my view is this: If God wanted us to view photos and images vertically, our eyes would be aligned likewise on our faces! :-D