Sudan-born Mr Atem, a PhD student at the Australian National University and former refugee, was shocked bystanders didn't intervene when the man unleashed the abuse, prompting him to question whether the ACT community had grown complacent about racism.

He was walking from the university to the National Library when he became aware of a man yelling abuse as he approached the lake not far from New Acton one morning last week.

"I saw a man walking in the opposite direction saying 'Don't let him in, he doesn't have an ID'. It didn't bother me, I just walked past but then when he said 'darkie' I realised he was talking to me and I was the subject of his ranting.

"He was yelling 'darkie immigrant, go back where you came from' and 'fake ID'."

Mr Atem, who was wearing a T-shirt depicting the Australian flag at the time, didn't take a lot of notice at first and said the man appeared to be homeless and could have suffered mental health problems.

But when he continued to yell at him for the next five minutes from several metres away, Mr Atem decided he would stand his ground and simply maintain eye contact.

"I was amused at first but there was a serious side to it.

"I though that if this guy is going to be so racist let's do it, I'm not going to run away and hide. This is my country too.

"We had this moment when he stopped where he looked into my eyes and I looked into his eyes and then he walked away."

Mr Atem said he was "a bit surprised" a man and a woman within hearing distance of the two men didn't do anything to intervene or question the abuser.

"Someone ranting at you for five minutes or so and these people walking past it and not doing anything is a concern. This is not all right - this is racism."

Mr Atem spent more than seven years as a refugee in Ethiopia and at a Kenyan camp before he arrived in Australia under the offshore humanitarian program 13 years ago. He's now studying the experiences of Sydney's South Sudanese community.

He had heard similar stories of racism from other members of the ACT's African community but had never experienced it until now.

"Is there something happening in Canberra? Has racism increased over the last few years in Canberra? If the answer is yes then what has happened over the last few years?"

If he could send a message to the man who abused him, he said it would be this: "We are all human".

"Unless you are Indigenous all of us have migrant heritage.

"We are all equal and we do our best to live peacefully and harmoniously and we can all contribute equally."