“I had to prove I was a citizen of New York, so I stabbed him” (joke)

New York City has a reputation as a violent place (or at least it had that reputation in the 1970s and 1980s). The comedian Emo Phillips told this joke on his album, E=MO² (1985):
 
“New York’s such a wonderful city. Although I was at the library today. The guy was very rude. I said, ‘I’d like a card.’ He says, ‘You have to prove you’re a citizen of New York.’ So I stabbed him.”
   
 
Wikiquote: Emo Philips
Emo Philips (born 7 February 1956) is an American comedian famous for his eccentric appearance, surreal humor, and the bizarre cadence of his voice in the delivery of his lines.
 
E=MO² (1985)
New York’s such a wonderful city. Although I was at the library today. The guy was very rude. I said, “I’d like a card.” He says, “You have to prove you’re a citizen of New York.” So I stabbed him.
     
Straight Dope Message Board
The Emo Phillips Thread
LindyHopper
10-24-2001, 10:45 AM
(...)
I was at the New York Public Library, and I wanted to get a library card; the guy said “You have to prove you’re a citizen of New York”...so I stabbed him.
     
Google Books
Following the Wrong God Home:
Footloose in an American Dream
By Clive Scott Chisholm
Norman, OK: University of Oklahoma Press
2003
Pg. 358:
All this urban growth and calamity took place in two months, which later reminded me of a quip by Emo Philips: “When I joined the New York Public Library, the guy told me I’d have to prove I was a citizen of New York, so I stabbed him.”
 
Google Books
How to Get Sued:
An Instructional Guide
By J. Craig Williams
New York, NY: Kaplan Publishing
2008
Pg. 49:
New York’s such a wonderful city. Although I was at the library today. The guy there was very rude. I said, “I’d like a card.” He says, “You have to prove you’re a citizen of New York.” So I stabbed him. —Emo Phillips