"I don't really understand what all the debate is about because it doesn't matter how far it goes; it is about getting it in the hole".
The Englishman was later joined on the top of the leaderboard by Japan's Hideto Tanihara, who also managed to keep the bogeys away from his six-birdie card.
Sharma, who won the Joburg Open last month for his maiden victory outside India as a professional, had four birdies against two bogeys in the second round.
"I did everything really well", Johnson said.
England's Justin Rose, the second highest ranked player in the field at No.6, was one better at 71, while No.9 Henrik Stenson finished on two-under par 70.
"I'm not saying that's why I'm playing well, but I took it really chill and the golf courses haven't changed, " Johnson said.
"Then on 17, it just felt like you could just touch that putt and it would go in, and after having Happy Birthday sang to me twice, I think the moment was made! Past year was the first time being here, obviously playing four rounds in the tournament definitely helps", said Johnson.
"You can't win the tournament after two days, you can only play yourself out of it. It's starting to pay off and I feel like I'm in a good position".
"It was nice. I was excited to get going".
" I feel like I got what I deserved on the last for staying so patient and it was nice to finish with a three, leapfrog a few guys and get myself into contention for the weekend". "It's not really a debate for me".
"I was standing beside the tee box while Rory, Tommy and DJ were hitting off and my legs were like jelly".
Johnson said he was eager to get back to Augusta National and compete in the Masters after missing the event a year ago when he reportedly slipped on a wet staircase and hurt himself on the eve of the tournament. On the back nine, he found his composure and birdied 10th and 11th and added another on 18th, just like the first day.
As for his other-worldly shot, Murphy explained it as if he did so every week - just like the big boys.
Dustin Johnson's 64 was remarkable given he, like McIlroy, struggled on the greens.