The 35-year-old American, who won the world title in 2005 a year after winning the Olympic gold in the Athens Games a year earlier, said he had done his time in serving a four-year ban (2006-10) for doping.
The prospect of Gatlin becoming world champion had made Sebastian Coe, prior to him becoming president of the sport's governing body the IAAF, feel "queasy". And the American had been roundly booed when it was announced he had won with Bolt in third.
Whle Gatlin raised a finger to his lips in defiance of their jeering, the crowd then chanted Bolt's name.
However, Gatlin insisted he was "no bad boy" and said he should be treated like anyone who is given a second chance by society.
"I'm just a runner," said Gatlin.
"I'm back in the sport. I've done my time and I've come back.
"I've done community service, I've talked to kids, I've actualy inspired kids to walk the right path.
"That's all I can do. Society does that for people who make mistakes. That's why I'm still back in the sport, still running and believe in myself."
Bolt, who said he would not be rethinking his plans to retire after his stellar career, also defended Gatlin's right to compete although the Jamaican had not been so generous when another American, Tyson Gay, had tested positive and then returned.
Mutual respect
"He's done his time and if he's here it means it's okay," Bolt said of Gatlin.
"I always respect him as a competitor. He's one of the best competitors I've ever competed against.
"He deserves to be here because he's done his time and has worked hard to get back here. I look at him as any other athlete."
Bolt also called "disrespectful" a suggestion that overall slow seasonal times were linked to a more efficient anti-doping testing programme, saying it was more down to either injuries, loss of form or even negative wind.
Gatlin, though, tried to shrug off the hostile reception he had received throughout the qualifying rounds and then when he won.
"Not at all, this was Usain's night, his last race," said Gatlin of the boos when he won.
"He has my utmost respect and this was his night, win or lose.
"He is still the man.
"I guess they booed me because I have become such a rival for him.
"There were no boos from 2010 through to 2015, but really I got the most pleasure from the way I stuck in there and came back."
Gatlin said he didn't know if he would call it a day now that he had succeeded in beating Bolt in a championship final -- just his second win over the 30-year-old in 10 meetings.
"Look, when I got the four-year ban I thought I was through and then I decided I should come back and resume training and see how it went," he said.
"For a millisecond when I crossed the line tonight I thought of retiring but now I wll see the season through."
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