The Uruguay international, who was booked the previous week at Sunderland for such an offense, could have had a penalty in Sunday's 2-1 defeat to Manchester United after a tackle by Jonny Evans.
However, his appeals were turned down by referee Mark Halsey and both Gerrard and Johnson believe the 25-year-old is suffering from the label given to him during a difficult period last season.
"I think even when Luis does get blatant penalties now he doesn't get them," Gerrard said.
"It is down to referees to not judge him and give what they see -- if it's not a penalty don't give him one but if it's clear give it," Gerrard said. "He was booked at Sunderland but against United it was a penalty."
Johnson echoed the sentiments of his captain by adding: "Everyone has to do their job: they have to forget about who they are looking at and make their decisions and not let anything from the past affect their decision.
"They have to call the shots at the time, regardless of who it is."
Johnson found himself on the receiving end when he conceded the match-winning spot-kick at Anfield after Antonio Valencia went down in the area.
The England right-back was fuming as he claimed he did not touch the Ecuadorian, whom he accused of cheating.
"I've watched it 50 times -- not that I needed to -- because it wasn't a penalty, I didn't touch him, I have collided with Pepe (Reina)," Johnson said.
"Reputations go in front of people at times and because Valencia is not a known diver that is why he got the decision. I almost guarantee if it was exactly the same situation and it was Luis and not Valencia then it wouldn't be a penalty."