“The difference between the Boy Scouts and the Army is that the Scouts have adult supervision” is a joke that was cited in a 1970 book about he Vietnam War. “Army” is often replaced in the joke with “Marines” or “police force” or even “Apple Computer” (in the early 1980s).
 
The joke is frequently credited to American stand=up comedian and Vietnam War veteran Blake Clark (born in 1946), but it’s likely that he repeated a joke that he’d heard in Vietnam. Clark’s entertainment career didn’t take off until the 1980s.
   
 
Google Books
Salmagundi Vietnam
By Don Pratt and Lee Blair
Rutland, VT: Charles E. Tuttle Company
1970
Pg. 45:
A VETERAN first sergeant, serving with an aviation unit in the Mekong Delta, claims that the only difference between his outfit and the Boy Scouts is that the Boy Scouts have adult supervision!
 
Google News Archive
19 March 1980, The Hour (Norwalk,CT), “Candidate Uses Flower Power,” pg. 18, col. 2:
WEST LIBERTY, Iowa (UPI)—Dan Ehl, who describes himself as one of the “hippies from the ‘60s,” has MuscatineCounty in a stir over his race for sheriff.
 
Considers some of his pronouncements:
 
. “The only difference between the police force and the Boy Scouts is the Boy Scouts have adult supervision.”
 
Google News Archive
5 December 1986, The Ledger (Lakeland, FL), “The president is in over his head” by Horance Davis, pg. 14A, col. 3:
The difference between the WHite House and the Boy Scouts is that the Boy Scouts have adult supervision.
 
Google Books
1,911 Best Things Anybody Ever Said
Edited by Robert Byrne
New York, NY: Fawcett, Columbine
1988
Pg. ?:
247
Being in the army is like being in the Boy Scouts, except that the Boy Scouts have adult supervision.
Blake Clark
 
Google Groups: rec.humor
Marine Humor
Wayne Wood
9/13/90
(...)
so, what’s the difference between the Marine Corps and the Boy Scouts?
 
1] Boy Scouts have adult supervision
2] Boy Scouts don’t have heavy artillery.
 
Google Books
Steve Jobs The Man Who Thought Different
By Karen Blumenthal
New York, NY: Bloomsbury Publishing
2012
Pg. 119:
But there was a joke that was popular in Silicon Valley: what’s the difference between Apple and the Boy Scouts?
 
The answer: the Boy Scouts have adult supervision.
 
Vanity Fair
12:00 PM, AUGUST 16 2014
What Combat Veterans See in Ferguson, Missouri
by Matthew Farwell
(...)
There’s a stale old joke—the difference between the Boy Scouts and the Army is that the Scouts have adult supervision—but on Thanksgiving Day, 2006, my Lieutenant proved that wasn’t true. As I observed the chaos in Missouri this week, I kept wondering where the adults were.
 
Twitter
John R. Fulton Jr.
‏@fultonjr
Right. What’s the difference between #Ferguson Police and the Boy Scouts? Yup - the Boy Scouts have adult supervision.
#FergusonShooting
1:17 PM - 18 Aug 2014