Those stories and this have the same central theme.

The belief that they are the most important person in the room, and everyone else exists to cater to them unconditionally. For redditors its the parents who legally couldn't kick them out (and often don't want to emotionally after they can), while Zelly boy its because "wahhh muh war."

With that assumption in place, they feel safe in all sorts of tantrums that logically make no sense without them.