It's wrong to act rudely toward mentally challenged folks.
Danny was watching his kids play at the park, when a bigger kid came along and took a toy away from one of his children.
Danny has to get the toy back for his child.
Danny walks over to the bigger kid, and it becomes apparent that the child is developmentally challenged, Danny decides to let him keep the toy.
Danny yells at the bigger kid and tells him to give the toy back, he also refers to the older, bigger child as stupid.
The child is happy and befriends Danny's children, while Danny is thankful that he controlled his temper and didn't say anything inappropriate.
The bigger kid gets upset and tells his parents, who come to let Danny know that he is developmentally challenged and not stupid, and Danny feels awful.