Salah had a touchline spat with manager Jurgen Klopp while coming off the bench in a 2-2 draw with West Ham.
Post-game, Salah walked by reporters and stated: "There is going to be fire today if I speak."
"I appreciate his (Salah) honesty because, the thing is, the only person that loses is him," Johnson told Squawka.
"If he speaks his mind and tells you what's really on his brain, then everyone's going to criticize him for it and he can't win. So that's why players shouldn't do interviews when they're fiery, or angry, or have just come off the pitch, or were sent off. Because they're going to speak from the heart. And some people aren't designed to take that.
"So I don't mind it. At least he's calculated and he knows that he's going to say some stuff that's going to upset people, so I'm sure he's told the people that are upsetting him in person.
"I respect it. I'm sure he's let his steam off elsewhere. Obviously, other fans and the press would love him to do it, for them. But it isn't about them. I'm sure whatever he's got to say is for the benefit of the manager and the team."