WA Nobel laureate Barry Marshall has weighed into the debate about planned changes to the Racial Discrimination Act, saying all Australians were bigoted "in some way" and legislation forbidding them from expressing an opinion was wrong.

In response to criticism of Attorney-General George Brandis' declaration that people have a right to be bigots, Professor Marshall tweeted yesterday: "I'm one. Sorry!" Posting a link to the Wikipedia definition of bigotry, he said: "People who are intolerant towards the Attorney-General on the basis of his opinion are; guess what!!??"

The website defines a bigot as "someone who, as a result of their prejudices, treats or views other people with fear, distrust, hatred, contempt, or intolerance on the basis of opinion, ethnicity, race, religion, national origin, gender, gender identity, sexual orientation, disability, socioeconomic status, or other characteristics".

Professor Marshall, who worked in the US for years, told _The West Australian _he favoured a US approach to free speech, where it was "quite OK to have people expressing different opinions".

"I may not agree with them but I don't go rioting in the street when I hear somebody saying something I don't agree with and I don't necessarily pillory them in public," he said.

He said by definition everyone was probably a bigot, including himself.

"There are people who set themselves up as judges of who are bigots and who are not, so all I was saying (on Twitter) was that I admit I'm a terrible bigot," he said. "There's bound to be stuff I'm prejudiced against and aren't we all."

For example, he said, Australians routinely said things about Americans they would not publicly say about other ethnic or religious groups.

"So Australians need to look at themselves a little bit and admit they are all probably bigoted in one way or another," he said.

Professor Marshall said the Federal Government had the "right attitude" with planned changes to the Racial Discrimination Act, which would repeal sections that make it unlawful to publicly "offend, insult, humiliate or intimidate" a person or group of people.

"As soon as I see legislation forbidding people from voicing an opinion I think that's wrong so on that basis I'd say that I think the Government's got the right attitude on this."