Rory McIlroy believes Justin Thomas will not be "as ignorant" in the future after the American made a homophobic slur while competing in Hawaii
Thomas apologised for using a derogatory word towards himself, which was picked up on TV, during January's Tournament of Champions.
The world number three has been dropped by one of his major sponsors.
McIlroy says Thomas "has learned his lesson", adding "he responded well, he made a big mistake and owned up to it".
Thomas will play with McIlroy and England's Lee Westwood in the first two rounds of this week's Abu Dhabi HSBC Championship event - the first European Tour event of 2021.
"He said he messed up; he's going to try to be better. And you know, Justin is true to his word. He will be," added Northern Ireland's McIlroy, who is playing on the European Tour for the first time in 14 months.
"I've got to know Justin really well and he is as good a guy as they come. He's got a lot of integrity, a lot of character.
"Obviously it doesn't make what he said any better, but in this day and age, it's hard because it seems like you're not allowed to make a mistake anymore. Any mistake gets jumped on."
Speaking publicly for the first time since his sponsorship split with Ralph Lauren was announced on Friday, Thomas admitted he was "upset" by the decision. "They have that right," he said.
"They had to make the decision that they had to make. I spoke with them along with all my sponsors.
"I apologised. It's an opportunity for me to grow and I felt like it was something we could have done together and gone through that process.
"They just felt like they needed to move on. That's exactly what I'm doing, as well."
Thomas reinforced his contrition over the incident which happened after missing a par putt on the fourth hole of his third round in Hawaii.
"It's humiliating. It's embarrassing. It's not me. It's not a word that I use, but for some reason, it was in there," he said.
"I'm trying to figure out why it was in there, and just like I said, it's going to be a part of this process and training programme or whatever I need to do.
"Not only to prove to myself but prove to my sponsors and prove to those people that don't know who I am that that is indeed not the person I am."
McIlroy, meanwhile, admitted to growing impatient as he seeks a first win since his triumph in Shanghai in November 2019.
"China in November 2019 does feel like a long time ago," said the 31-year-old world number six.
"I didn't really play that great coming back out of lockdown, but then felt like I was starting to play a lot better as the season came to an end.
"I'm trying not to be impatient. I try to stay as patient as possible, but what I will say is that last win does feel like quite a long time ago at this point."
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