LCR Honda rider Nakagami came under fire from Rins after the pair came together during the Italian Grand Prix and the latter crashed out of the race.
Then last Sunday at the Catalan GP, Nakagami crashed braking aggressively into Turn 1 having started 12th and wiped out both Ducati's Francesco Bagnaia and Suzuki's Rins.
Rins, who slammed MotoGP's stewards for taking no action on the incident, has been left with a left wrist fracture, while Nakagami was kept in hospital overnight having hit Bagnaia's rear wheel with his face.
The Mugello incident was brought up in Friday's safety commission at Barcelona, where Nakagami was largely defended for his actions, though it was agreed his overtaking can be aggressive.
But Zarco, who finished third at Barcelona, says the Japanese rider has "lost all his credit" following his Turn 1 spill.
"We spoke about it in safety commission, and from Mugello Rins asked our opinion on the accident they had together," Zarco said.
"He wanted to have our opinion on what happened and we were almost all agreed in that case Nakagami didn't do any mistake in Mugello and we are kind of agreed with the stewards that they cannot penalise Nakagami in that case, even if we were also agreed that Nakagami can sometimes be quite aggressive when overtaking.
"But he was not doing a huge mistake [in Mugello]. But from today he totally lost all his credit that we gave to him during the safety commission, which is a pity for him.
"I don't know what they're going to say, but overall he took out Rins and he has lost all his credit, which is a pity for him."
Barcelona race winner Fabio Quartararo also felt the crash should not have been deemed a racing incident and urged riders to be "conscious" of the dangers in first-lap encounters.
"It was not a racing incident, because you don't attack that much," Quartararo commented.
"I don't know how it is possible that Pecco was second and Nakagami was far away, how he can arrive to touch his head on the wheel of Pecco.
"It's not a racing incident. I think in the first laps we all need to be conscious that we are racing big bikes, that the weight is a minimum of 160 kilos and if you get hit by a bike like this you can pass away.
"And this is where the most dangerous place is for us, in the start, then after the first lap there is less risk."
Jorge Martin, who was second in the race, echoed Quartararo's comments, while adding that the stewards' decision not to penalise the Mugello incident has set a negative precedent.
"For me, it's not a racing incident. I think they should have penalised Nakagami already in Mugello, because he wasn't penalised and now he thinks he can do anything," Martin said.
"So, now he does it again and if they don't penalise him, he will do the same in the next race.
"So, it's dangerous for the rest. He broke Alex Rins' wrist, he risked also something important for himself, which was his head.
"They need to work out a system that helps the security of the riders, and for sure without penalising him is not the way."
