There's no affirmative duty to intervene if you're a non-crewmember in this situation.
Doing so will most definitely land you in a very expensive civil suit, and depending on how the video rolls and the perps involved, you could wind up with criminal charges from both state and local authorities.
It's a sit sandwich, that's for sure, but as a "rich airline pilot" with a big umbrella policy (you do have one, yes?), you're a primo litigation target.
There's more detailed (non video) link with names and some unintentionally funny quotes here:
https://news.yahoo.com/delta-passeng...212016524.html
"Seriously?" asks one passenger in the video as he places his hand to his forehead in exasperation. "I already missed one flight!"
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I'm actually amazed that a news site got their hands on the video, which airlines do a very good job suppressing for obvious reasons. I did notice that the included footage of the American Airlines passenger in cuffs was sanitized (face blurred) because of other obvious reasons (think "United in Chicago", several years ago).