I found this an appalling way to treat paying customers.
Watching the video, the family had paid for all its seats, the flight was overbooked. There was no counter offer discussed, i.e. a free hotel and cash.
Then Delta tries to twist the situation to their advantage by quoting safety regs by stating the 2 yr old must sit on the parent's lap for the duration of the flight, FAA rules apparently whilst Deltas own website clearly states 2 yr olds can travel in kids seats the parents had carried onto the flight.
https://www.youtube.com/watch?v=p7pM8IyxpTc