At the time Scotland only trailed 10-3 but playing for that long with one men less took its toll as Wales ran in seven tries in all, George North and Jamie Roberts both bagging doubles.
But despite the demolition, in Johnson's last game as head coach before the arrival of Vern Cotter this summer, the Australian refused to make Hogg a scapegoat for his side's defeat.
"Stuart might be many things, and one of them is a great character, but he certainly isn't a dirty player, that's for sure," he said.
"He's already been in to apologise to Dan Biggar and the referee. It's so totally out of character for him.
"He's really down about it. He's taking it tough. He's an emotional lad and that emotion is a good thing, and in this case he is feeling he has let the boys down.
"He's got to face reality that he has been caught doing something, he's got a proper tribunal to front and show his case. So he's in a dark place but that's just life. He has got to confront it.
"It wouldn't have been the same result, as in the scoreboard. I thought we were in the contest but full-back is a hell of a position to fill for that length of time.
"If it's a forward you can cover it but it's harder to cover a back division player, and once they were on a roll they played some pretty good rugby, too. But it felt like there was a lot of field to cover and was difficult for us."