“Congratulations for raising a 21-year-old and teaching them not to care or give a damn about the neighbors partying out loud and in fact being another dismissive and disrespectful human being. Great job!” the letter read.

The birthday person was told they should have been considerate of their neighbors if they planned on “partying until midnight”.

“I know your parents didn’t teach you that but please consider your neighbors when partying until midnight. I truly believe this is a milestone to be celebrated and hope you will never ever encounter neighbors like yourself in your life,” they wrote.

“If and when you decide to have a family or come home tired from work or even want to have the right to sleep peacefully in your own home, yes that is a right, please consider your neighbors.”

The letter went on to implore its receiver to “use your brain”.

“The world does not need another disrespectful human being,” it read.

They also said that the party host should have told neighbors about their plans ahead of time so that they could "plan/prepare for circumstances" and could have been taken to a club or restaurant.

On Monday, a picture of the angry letter was posted to The Bell Tower Times's Facebook page, where it got more than 600 comments. One man said he was the birthday boy.

“Thanks for the birthday wishes everyone. Just to clear up, flyers were sent out and definitely received,” he wrote.

“How else would they have known it was a 21st party?”

Most other comments came from people defending the party host and arguing 12am was a reasonable finish time.

“You mean they partied until midnight then it shut down without police intervention? They should count that as a success!” one wrote.

“Good grief! A 21st birthday party! That went till midnight! I’m shocked and horrified! So inconsiderate! *insert sarcasm font*,” another said.

“Some folks just need to get a life. If it was loud until 4am, fine. But sounds like it wrapped up at midnight. Good on them! Happy 21st,” a third wrote.