Madison Square Garden chairman James Dolan responded to a Knicks fan who had criticized him with an email wondering if the man is an alcoholic and telling him to root for the Nets instead.
An MSG spokesman confirmed the email, which appeared Sunday on Deadspin.com, was written by Dolan.
Dolan called the father of filmmaker Aaron Bierman a "hateful mess" and a "negative force" to anyone with whom he comes into contact.
"You most likely have made your family miserable. Alcoholic maybe," Dolan wrote. "I just celebrated my 21- year anniversary of sobriety. You should try it. Maybe it will help you become a person that folks would like to have around."
The elder Bierman had written Dolan and said he was a Knicks since 1952 who was tired of Dolan's management of the team and urging him to sell.
"As a Knicks fan for in excess of 60 years, I am utterly embarrassed by your dealings with the Knicks," he wrote.
Dolan has been in charge of the Knicks since 1999. He ended his response by saying to "start rooting for the Nets because the Knicks (don't) want you."