"I don't think it would be justified," said the sole surviving 617 Squadron pilot.
Flight Sergeant Johnson was a bomb aimer during the Dambusters mission that used ingenious 'bouncing bombs' invented and developed by Barnes Wallis, who was knighted in 1968.
Earlier this year, Mr Johnson, 92, publicly called for a medal to recognise the aircrews.
Now, a petition launched through Change.org by Stephen Hadley of Kent calls for Mr Johnson to be knighted, "In recognition for services and contribution to his country by displaying unconditional courage and gallantry in the face of the enemy and an inspiration to all of his fellow countryman".
Les Munro. Photo / APN
"It is shocking when you hear that David Cameron's hairdresser gets an award but someone like Mr Johnson has never had any formal recognition," Mr Hadley told the Bristol Post.
New Zealand aviation historian Paul Harrison believed Mr Munro was worthy of a knighthood. "Although he did not get to drop his bomb - his aircraft was hit by anti-aircraft fire [and] had to turn back - the mere fact that he was part of the raid should warrant recognition," he said. But Mr Munro isn't so sure.
The Kiwi war hero didn't believe that a special medal - let alone a knighthood - was warranted just for one raid.
"I didn't get one and I don't think I deserve one," said Mr Munro, whose flying exploits earned him several medals, including the Distinguished Flying Cross and Distinguished Service Order.
"I feel I have received enough recognition for what I was a part of."
Simon Moody, research officer at Wigram Air Force Museum in Christchurch, said while it was important for the Dambusters airmen to be properly recognised, it would be unfair to "single out" survivors with a knighthood.
"Les might say he was just one of the Bomber Command boys who went out every night and did his job," Mr Moody said. "The most important thing is tell the story, and to let them tell their story as well."
The Dambuster Raid
• Carried out by No 617 Squadron.
• 19 Lancaster aircraft left on May 16, 1943 carrying 133 men.
• 11 aircraft made attacks.
• Eight aircraft were lost and two aborted mission.
• 53 aircrew were killed and three taken as prisoners.
• Targets were Mohne, Eder and Sorpe dams, Germany.
• Motto: "Apres moi, le deluge" meaning "After me, the flood".
- Royal Air Force