“People fear what they don’t understand/know” (“fear of the unknown”) has been cited in print since at least the 1910s and is of no specific authorship. The saying has been used to describe those who fear new technologies. The saying has also been used by those who want to differentiate people’s fear of Islamic terrorism from fear of the Islamic religion.
 
The rapper Nas released “Hate Me Now” (1999) with the lyric:
 
“niggas fear what they don’t understand
hate what they can’t conquer”
 
The full expression, “People fear what they don’t understand and hate what they can’t conquer,” has been credited to Nas, but has also been credited to someone named “Andrew Smith.”
   
   
Wikipedia: Nas
Nasir bin Olu Dara Jones ( /nɑːˈsɪər/; born September 14, 1973), who performs under the name Nas ( /ˈnɑːz/), formerly Nasty Nas, is an American rapper and actor. The son of jazz musician Olu Dara, he was born and raised in the Queensbridge housing projects in New York City. His debut album Illmatic, released in 1994 by Columbia Records, was critically acclaimed and would go on to be widely hailed a classic in the genre. Nas was part of hip-hop supergroup The Firm, which released one album.
   
Wikipedia: Hate Me Now
“Hate Me Now” is a 1999 hip hop single by rapper Nas featuring Puff Daddy. The backbeat is inspired by, and contains some samples from, Carl Orff’s Carmina Burana.
 
Google Books
Race Orthodoxy in the South, and Other Aspects of the Negro Question
By Thomas Pearce Bailey
New York, NY: Neale Pub. Co.
1914
Pg. 163:
Worth incidentally has mentioned the true causes,—“dormant race-hatred,” “people fear what they do not know”; “three hundred tragedies” [mulattoes in an audience]; the mulatto woman who “passed as white.”
   
Google Books
1 January 1919, The Gas Age, pg. 47, col. 1:
People fear what they do not understand; and it is far better for a gas company to teach its consumers some of the fundamental facts about gas service than to have them learn half the truths from public agitators or from other prejudiced and colored sources.
 
Google Books
The Weekly Underwriter
Volume 136
1937
Pg. 737:
Revealing the groundless fear of devastating inflation in the United States, he pointed out the great stablity of our present credit standing and said in part : People fear what they don’t understand.
     
Google Books 
The Air-Conditioned Nightmare
Volume 1
By Henry Miller
London: Secker & Warburg
1947  
Pg. 172:
What is it that people fear? What they don’t understand.
   
Google Books
I, the Union:
Being the personalized trade union story of Hebrew Butchers Workers of America
By Joseph Belsky
New York, NY: Raddock
1953, ©1952
Pg. 142:
Realizing that people fear what they don’t know, I set about letting everybody know about me, the Union.
   
1 October 1954, Provo (UT) Daily Herald, “Cauterization Held Worse Than Dogbite” by William Brady,  pg. 12, col. 5:
The main point of all the mad dog publicity appears to be to keep people confused. People fear what they don’t know.
 
Google Books
Wage and Salary Administration
By David W. Belcher
New York, NY: Prentice-Hall
1955
Pg. 367:
It has been repeatedly demonstrated that people fear what they don’t understand.
 
Google Books
Toward a National Urban Policy
Edited by Daniel P. Moynihan
New York, NY: Basic Books
1970
Pg. 328:
People fear what they do not understand, and the command of technological skills among critics of technology has tended to be minimal, hence the presumption that warnings of disaster, while interesting, were at the same time…
 
Google Books
Introduction to Data Processing
By Carl Feingold
Dubuque, IA: W.C. Brown Co.
1975
Pg. 249:
People fear what they don’t understand. The rank and file basically fear for their security when confronted with system change and improvement.
 
Google News Archive
21 December 1981, Lewiston (ME) Journal, “Meet the women of DEP,” pg. 22, col. 5:
“It’s basically a communications problem,” Bradford observes. “People fear what they don’t understand.”
   
Google Books
Business Technology for Managers:
An office automation handbook
By Neil Perlin
White Plains, NY: Knowledge Industry Publications
1985        
Pg. 116:
People fear what they don’t understand and, while people live with technology, few understand it.

Google Books
In Love and War:
The story of a family’s ordeal and sacrifice during the Vietnam years
By James B. Stockdale and Sybil Stockdale
Annapolis, MD: Naval Institute Press
1990
Pg. 478:
“It’s deplorable that so many people fear what they don’t understand. I guess overcoming that is what education is all about.”
 
Google Books
Sunrunner’s Fire
By Melanie Rawn
New York, NY: Daw Books
1990
Pg. ?:
“It’s damned inexplicable to somebody like me. People fear what they don’t understand.”
 
Salon 
Tuesday, May 11, 1999 12:00 ET
Sharps & flats
Reviews of new releases from Nas, Matthew Shipp and a new Neil Young tribute.
Nas “I Am”
Columbia
By Jeff Stark
(...)
Structurally, “Hate Me Now” is an entire hip-hop album in miniature. It begins with an introduction announcing, “Escobar season has returned,” and drops some nonsense about life or death and blah-blah-blah over the top of the sampled cheers of teeming millions. Then, at the mike, appears the cameo marker of almost every rap record released in the last three years: Puff Daddy. (Yeah, he’s corny, but Puffy is still hip-hop shorthand for mega party single.) Puffy can’t rap, which Nas seems to understand, casting him to sort of half sing the simple chorus: “You can hate me now/But I won’t stop now/‘Cause I can’t stop now.”
 
Nas, for his part, spits words like he’s spraying bullets. “Niggas fear what they don’t understand/Hate what they can’t conquer,” he raps.
 
Only Lyrics 
Don’t Hate Me Now by Nas [R’n'B Single Release Promo 2006]
(...)
ambulances were picking them up niggas fear what they don’t understand
hate what they can’t conquer
guess its just a theory of man
became a monster, atop of the world
never fallin
I’m as real as they come
from day one, forever ballin
c’mon
     
Naija Ryders
LadyAmbition
11-23-2003, 05:20 PM
People fear what they don’t understand, hate what they can’t conquer.—-Nasty Nas
     
The Magic Cafe Forum
Che
Posted: Mar 3, 2004 12:26pm
(...)
BUT, as the saying goes; “Men fear what they don’t understand, HATE what they can’t conquer”.
   
Second Life Forums 
Suspiria Finucane 
Re: is the emerald download site down.
04-21-2010 12:52 AM
“People fear what they don’t understand and hate what they can’t conquer”.
Andrew Smith
 
Top Wire News
SEO for Lawyers using Legal Blogs by law firm internet marketing experts
August 26, 2010 (TopWireNews.com: - press release)
August 24, 2010 - Dallas, TX - In the past lawyers who have not understood legal blogs have avoided them in fear that they were unethical for law firms to use as a marketing medium. This fear is based on half truths and an overall lack of knowledge. In the word’s of Andrew Smith, “People fear what they don’t understand and hate what they can’t conquer.”