The clip in question sees Thomas, who was the creator, writer, star and occasional director of his cult hit series Please Like Me, discussing difficulties in casting actors from diverse backgrounds.
Warning that "this is going to sound racist," Thomas said, "most of the immigrants in Australia have come pretty recently, and generally, first or second-generation immigrants don't want to be actors. They have real jobs.
"The other thing I didn't know about making a TV show that I found quite confronting is you have to pick every person. 'Josh, what do you want the 7-11 worker to look like?' Do you make them Indian, or is that offensive? Or if you make them white, is it a bit like you're lying, really? What do you do?"
"But also, it's taking a job away from an Indian actor if you don't," Pacquola said.
"What answer is not offensive?" Thomas pondered, prompting an interjection from McGregor acknowledging the all-white panel: "We're probably not going to come to the answer with this panel."
Community and Rick And Morty creator Harmon then spoke about efforts in Hollywood to make TV writers' rooms more diverse, before Thomas interrupted.
"I feel like I just tried to say this and they thought it was racist, so I love that you're doubling down on it … Finding people who have been given the same opportunities to be great at acting is really hard. None of the other shows are hiring people that aren't white. Finding an experienced actor that's not white is really hard. You find yourself in a situation where you want to be more diverse, but this person doesn't have as much experience as this person, and then it's hard to know what to do, because you don't want to be favouring people when they're not going to do a good job."
"In the States, the answer is you have to look harder," Harmon said.
The clip sparked an immediate reaction among those seeing it for the first time online:
Others came forward to say they were in attendance at the event:
"Dude I can absolutely confirm this. I saw it live, it was a total **** show even then!" replied comedian and actor Nina Oyama.
Actor Johnny Lahoud shared a Facebook status he'd written in December 2016, immediately after walking out of the audience for the panel session in disgust over Thomas' comments.
As the clip spread, Thomas issued a Notes app apology, saying he was being a "really dumb, illogical, insensitive idiot".
"I'm super ashamed of the comments I made, and would like to apologise," he wrote.
"The answers I offered in this clip are in no way constructive or correct. I am committed to doing better."
