"What other people say is irrelevant," he says at one point during his media briefing at Murrayfield. Then, just to make it clearer, he adds: "I don't really care what other people say."
But as the point seems to be going over the heads of some in his audience, he then nails it beyond all doubt. "To be honest, I wouldn't give a rat's arse what anybody is saying," he says forcefully. "I don't give a rat's arse. It doesn't worry me at all. How's that?"
Good enough. And perhaps not a bad standpoint for a man who will be something of an opinion magnet and a lightning rod for criticism over the next few months. Whether Johnson cares two hoots, or a rat's arse or anything else is of no great consequence as the Six Nations Championship hoves into view. It is going to happen anyway.
Johnson was the obvious, and in some eyes only, candidate to take over when Andy Robinson fell on his sword after Scotland's humiliating 21-15 loss to Tonga at Pittodrie last November. He says now that he will examine his long-term options at the end of the Six Nations, but cynics might suggest that he is only getting his excuses in early. And as his record as Wales' caretaker in 2006 was played three, lost two, drew one (at home to Italy), the cynics might just have a point.
It was while with Wales that Johnson first had dealings with Dean Ryan, who has come in to do a shift, strictly limited to 12 weeks, as Scotland forwards coach. At the time, Ryan was looking after the affairs of Gloucester, where a couple of Welsh players were plying their trades.
"I had spent a couple of afternoons with him," Johnson says. "We had mutual friends. He has rugby knowledge, is a good forwards coach and a good bloke. A few boxes ticked there. You come across good and influential people in the game and I was lucky he was available."
In truth, it is hard to think of many coaches with appropriate experience who would take on what Ryan has just signed up for. So little time, so much credibility to lose. But as the former England No 8 has made it clear that, for personal and family reasons, he has no ambition to return to full-time coaching, he could be just the figure Scotland need.
Already, one decision appears to have been made. The half-backs are the hinge for any team, and Johnson and Ryan seem to have settled on Greig Laidlaw and Ruaridh Jackson as the men they will send out, fitness allowing, against England in three weeks' time. Jackson gets the nod at fly-half because his recent form with Glasgow has been sound; Laidlaw returns to the scrum-half berth because the one part of Jackson's game that is still missing is his goal-kicking.
As Jackson had fallen out of favour with Robinson and Laidlaw had been deployed primarily in the playmaker's No 10 berth, it seems a radical change of tack. But it isn't. Both have looked more at home in those berths for their clubs in recent weeks, even if Laidlaw will be back at fly-half for Edinburgh against Munster at Murrayfield today.
Johnson says: "I am not going to lie here. We have made a decision with Greig where we see him as a nine who can play 10 rather than a 10 who can play nine. It's important for him to know that.
"One thing I will say about Greig Laidlaw is he is one hell of a kid and one hell of a competitor. The fact is we'd like to see him in that squad and he adds value to that team and we're trying to find where that is."
It might not sound the most ringing endorsement in history, but Johnson's messages behind the scenes are presumably stronger and more encouraging. An examination of his results with Wales, Australia and the USA produces a decidedly mixed picture, but he is consistently successful at winning the affections of the players he works with. That support may not ensure success, but the lack of it would probably guarantee failure.
Johnson also admits his options are limited. "Let's be honest," he shrugs. "It is what it is. These are the players we have to pick from. We've got X and Y and we've got to work with where we are.
"We have let ourselves down in certain areas of the game. If Andy was sitting here, he would be saying the same thing. The reality is we've got to work on the areas of the game that need improving and we are deluding ourselves to think otherwise.
"The panacea for this group and country doesn't lie in trying to be New Zealand. It's trying to be who we are and do what we do better. In the autumn games there were certain periods where everything shone. The reality is we have got to do more of that."