His mother Jeanette and father Willie Gatlin, who are staying in a Copacabana hotel, pleaded for the haters to leave their son alone - saying the public did not understand the matter and had wrongly targeted the 34-year-old New Yorker.
His mom said: 'We have sat back and listened to people who are sadly misinformed and believe every sensational thing they hear. They don't know our son.
'Justin is not a quitter. He is a fighter. What happened here (the cat calling and booing) has not affected him.There is nothing negative about him.
'If that was the case, he would have stopped a long time ago. He would have given up in 2012 or in 2015 in Beijing. But he is the strongest person I know.'
She added: 'In my heart he has achieved everything and made history in many, many ways. He is a hero to me. He is up there.
'He is at the top of his game and the last person to beat Usain Bolt was Justin Gatlin in Rome 2013.
'There is nobody else in the United States that's there.'
Gatlin's father said his son had been wrongfully convicted of doing offenses and the system had worked against him, even though he had served his punishment.
They cited cases of jailbirds who committed criminal offenses and yet had the slate wiped clean after serving their sentence.
"Justin has never committed any crime and yet he stands there taking all this,' he said.
After finding global fame when he won gold in Athens, the sprinter failed a 2006 test for testosterone. He claimed his masseuse had rubbed cream on him containing the banned steroid, but he served a four-year ban.
He returned to competitive athletics on 2011 in better shape than ever.
It was the second controversy to descend on the 34-year-old track star - who has never admitted to doping.
In 2001 he was banned from international competition for two years after testing positive for amphetamines.
But he later successfully appealed that the positive test had been due to medication that he had been taking since his childhood, when he was diagnosed with attention deficit disorder. The ban was later reduced to one year.
His father said: 'The medication was never on the (banned) list. They only put it on months after.
'So even if we were watching the list at that time, it didn't matter because it was never on the list. But they don't say that.'
His mother added: 'It was medication he had been taking since he was nine years old. It should never have happened.
'They had all the medical records. They should have cleaned his record. He was in school, he took his medication to study for his finals.'
They were adamant that their son had been wrongly accused, found guilty and was still being punished for the alleged offense.
She added: 'Justin has to be himself. He has to do what he needs to do. He focuses and trains very hard.'
Asked if he might retire after Rio, she said: 'He would have to be the one to answer that.
'But he says, "I know what I did and I know what I didn't do. I cannot change people's minds. I am not going to try all I'm going to do is what I need to do. Be focused, train hard and get out there and run."'
She added: 'He is the strongest person I know. I am proud of Justin because I know his character.
'I know the person that I gave birth to. We have other children and you know all of your children. He is a good kid.
'He is always expressing his love for us. We got texts today. He was checking on us and he wants us to be happy and enjoy Rio.
After personally witnessing the spectator attacks on him, their son tried to console them saying: 'Don't be sad, don't let anything bother you. Get out enjoy Rio and have a good time.'
After he lost in the 200m, Gatling appeared to dismiss the suggestion that he had been affected by the response from spectators in Rio.
He said on Wednesday: 'It's a showman's sport. I think the rivalry that I have with Usain, it's turned it into a professional wrestling feel.
'Everyone's cheering for Usain, but they have someone they have to boo against.'
Tracy Sundlin, who is in charge of the US track and field men's team, said: 'Justin is a remarkably talented athlete who clearly made a mistake at some point.
'He has paid dearly for that mistake. He has owned up to that mistake.
"If people saw what he is doing and the amount of effort... if they saw his heart, I think they would feel as I do.'
