oh boy...
What is wrong with you people? It wasn't just swap seats for fun or something else. They clearly saw that the swap was for child and the safety/comfort other passengers.
no, the swap was because you didn't want to give up your complimentary upgrades. you are asking people to inconvenience themselves for your benefit, and **you complain because someone does it, but not with the attitude you want while they're doing it**. "what is wrong with you"?
I also blame Delta since it was their responsibility to accommodate child and mother together
which they were willing to do. but you weren't willing to go with the solution they had available (coach).
Moreover, I believe that all of them got their seats as a complimentary upgrades as well.
you have no idea whether this is actually true.