1K should have been moved, preferably back to y. Moving 1L before any trouble occurred is outrageous. Inconveniencing a parent busy trying to make life better for everyone on the plane is selfish and tactless.

1K and anyone else should read the conditions of carriage and note pax have no say on who they sit next to. If they do not like what they see they should rent a private jet. Shame on UA for not siding with the parent.