Tim Soutphommasane's intervention in the debate will come in a speech he will deliver at the Australian National University, where he will warn the proposed change may ''licence racial hatred''.

''It may encourage people to think there is no harm in dealing out racial vilification,'' he will say, according to a copy of the speech obtained by Fairfax Media.

He will contest the notion there is a compelling case for change and criticise those he labels the ''thick skin brigade''.

''[They say] let good speech override bad speech, let there be an open contest and put our faith in the goodness of our fellow citizens … There is in such arguments a certain naive optimism,'' he says. ''We cannot realistically expect that the speech of the strong can be countered by the speech of the weak.''

Victims of racial abuse may absorb the message of hate and inferiority. ''Those who are unfamiliar with the wounding power of racism may dismiss this as superficial complaints about words,'' he says.

''There remains what I call the 'thick-skin brigade' - those who would declare, 'sticks and stones may break my bones, but words can never hurt me'.

''This is the brigade that believes the only racism that warrants our public attention is the kind that involves physical violence, that believes racial vilification is at best an ersatz racism that troubles only effeminate citizens concerned with inconsequential feelings.

''Members of the 'thick-skin brigade' belong to the middle ages, to a time when the law was indeed confined to offering remedies only for physical interference with life and property, when the law only recognised that liberty only meant a protection from battery, when property would still be referred to as land and chattels.''

Dr Soutphommasane will use the speech to put ''a human face'' on racial vilification. He says a person who witnesses an ugly incident of racism may gain a new appreciation of the harm it causes.

''It is not clear to me, at least, how someone who has been called a 'coon' or 'boong' or 'gook' or 'chink' or 'curry muncher' or 'sandnigger' should be grateful to a bigot for giving them the opportunity to improve their soul.

''It seems perverse to say that we must all tolerate hate, when not everyone has to bear the burden of tolerance in the same way.''

Dr Soutphommasane says the proposition that any restriction of speech is demeaning, even to those it aims to protect, does not stand up to scrutiny.

''In the current debate about the Racial Discrimination Act, numerous communities have spoken out against any change to existing legislation,'' he says.

''To the views put forward by those who believe any restrictions on speech can demean and offend the dignity of those whom we desire to protect from harm, we may question what is more likely to amount to infantilising our fellow citizens. Is it to have protections against hate speech? Or is it to tell some communities that in spite of what they say, that we may know better what is in their interests?''

Dr Soutphommasane was appointed by the Labor government in July to oversee the Racial Discrimination Act.

The controversial section is 18C which makes it unlawful to do something reasonably likely ''to offend, insult, humiliate or intimidate'' someone on racial grounds.

Conservative commentator Andrew Bolt fell foul of this section in 2011 after accusing several fair-skinned Aborigines of identifying as indigenous to claim benefits only open to Aboriginal people.

In 2012 Mr Abbott said if the Coalition won the election he would repeal section 18C ''in its current form''. Attorney-General George Brandis has pledged to amend this section.