I wish my family got along at Disneyland, but they don't. Last time we went as a family (my brothers and sisters are all grown), we absolutely couldn't stand each other.
When we were little, we always got along at Disney though. Maybe it was because my parents taught us public manners and we knew that if we fought, we would go home in an instant. My parents also knew to take time outs during the day which helped enormously to calm down the tempers. I wish more parents would do the same these days.
Maybe the park just intensifies ones true feelings of the day. I don't know why some families seem to bond and others don't while in the park.