Latrell Mitchell's former coaches have warned racial abuse directed at the star fullback is just the tip of the iceberg, with Trent Robinson pointing at systemic issues within Australian culture.

Robinson on Friday apologised to Mitchell on behalf of the Sydney Roosters, amid claims a fan wearing the club's jersey was allegedly the fan who abused him at Penrith.

Both the NRL and NSW Police are investigating, amid calls from Robinson, South Sydney and past and present players for a lifetime ban for the perpetrator if guilty.

Mitchell debuted at the Roosters in 2016 and won two premierships at the NRL club before his exit for the Rabbitohs at the end of 2019.

"It's really disappointing. We just don't represent the Roosters in that way. It's not how we want to act as Roosters," Robinson said.

"Whether we like it or not, they were wearing our colours. We have to accept that. But it doesn't mean they are a Rooster.

"If you want to act like that, and abuse people racially like that, then that is not who we are. It's not who we want to be.

"We need to be better than (that). I'm apologising from the Roosters to Latrell, even though it's not directly us. Indirectly one of our fans did that, and it's not right."

Robinson did, however, admit he was not surprised by the situation.

"Because that's where we are still at as a country," Robinson said.

"It's pretty standard. Some people are casual racists and some people are overt like it was last night. That's where we're at.

"People don't like strong Indigenous voices like Latrell. They would rather he stay quiet and in his box and not express it in that way.

"We are still not at a point where we are able to accept really strong Indigenous voices in this country. That's really disappointing."

Mitchell's former coach at Souths, Wayne Bennett, also warned this was not an isolated event.

"I've been around a lot of Aboriginal players my whole coaching career and I can tell you that Latrell is not the first one it has ever happened to," Bennett said.

"We don't like it. We don't believe in it but that's the situation.

"It is not acceptable in our game and that's all we can control."

Regardless, Robinson played down fears the 25-year-old could be driven out of the game after watching him confront online trolls publicly in 2019. .

"He's too strong for that," Robinson said.

"He will get stronger and stronger from this. This isn't the first time we've seen it with Latrell.

"He will use it in his way and the right way."