"All the necessary mea culpas have been made copious times, so for this question to keep coming up, it's kind of like ... I'm sorry they feel that way, but I've done what I need to do," he said.
Last month, Gary Oldman defended Gibson's outburst in a controversial Playboy interview, for which he later apologised.
"I don't know about Mel. He got drunk and said a few things, but we've all said those things," said Oldman.
"We're all f****** hypocrites. That's what I think about it. The policeman who arrested him has never used the word 'n*****' or 'that f****** Jew?'"
The Batman actor wrote an apology letter to the Anti-Defamation League, then went on US chat show Jimmy Kimmel Live to say sorry publicly.
"I am a public figure, I should be an example and inspiration and I am an arsehole," he told Kimmel.
"I am 56. I should know better. So to them, my fans, I say I extend my apology and my love and best wishes to my fan base."
Gibson has since spoken out in support of Oldman, describing him as a "good guy".
"These things happen. As we all know ... I have nothing much to say. The guy was probably just ... He's a good guy," he told Variety.
"He's fantastic. I know him. He's a good dude ... I didn't even look too hard."
- Independent