According to a Herald ReachTel poll, 63 per cent of voters want to restrict Sydney's migrant intake. A poll by The Australian Population Research Institute last year found 54 per cent of voters wanted a reduction in immigration. These are big numbers questioning Australia's migration levels. Politicians, however, are sticking with high growth.

Both the Coalition and Labor parties are bolstered by Treasury’s insistence in boosting aggregate GDP. This is no matter what it costs in the real terms of overdevelopment, congestion and unaffordable housing. And business lobbyists, too, are keen to profit from an ever-growing domestic market.

Almost two-thirds of respondents want Sydney's migrant intake restricted. Daniel Munoz

The major parties ignore voters’ preferences because they can, believing voters have nowhere else to go. They may also be reassured by a dearth of effective public criticism.

Why this dearth? Taking voters’ concerns seriously risks breaching norms of polite discourse established and enforced by the group French economist Thomas Piketty calls the Brahmin class. These are left-leaning intellectuals with clear ideas on what may not be said on questions concerning race which, for many, includes questions about immigration.

This acts as a muffler on serious public debate.

The TAPRI survey, which I oversaw, asked voters: "Do you think that people who raise questions about immigration being too high are sometimes thought of as racist?" Sixty-five per cent said "yes", 26 per cent said "no" and 10 per cent said "don’t know".

Those who said "yes" were then asked if this was because such people really were racist. Respondents who agreed made up 20 per cent of the whole sample and were termed "guardians against racism". In contrast, many said that the accusation was "unfair because very few of them are racist". They were 45 per cent of the sample and were termed "the threatened".

Voters who said "no" were "the fearless" while those who said "don’t know" were "the confused".

University graduates were more likely to be guardians, and non-graduates more likely to be threatened.

We then asked: "Have you yourself ever felt uncomfortable about raising questions about immigration, for example with friends or workmates?"

There were five response categories including: "Yes, people can get the wrong idea about you if you do". The threatened were much more likely to chose this response, especially if they were graduates.

This may seem counter-intuitive. But as graduates they are more likely to meet guardians in their daily lives and so more likely to feel at risk. The irony is that even though 26 per cent of graduates were guardians, 37 per cent of graduates were threatened.

Some unsympathetic commentators disparage Brahmins by calling them the "chattering class". Mark Lopez says we should also talk of a "whispering class", well-educated professionals who don’t share all of the Brahmin agenda. But they know that they must keep their voices down or risk opprobrium and exclusion.

The institute study found that 65 per cent of voters are aware of the taboo on criticising immigration and that many are inhibited by it. While non-graduates are more likely to feel the threat, a substantial proportion of graduates are also conscious of it.

Bipartisan support for high migration, backed by a vocal and cashed-up growth lobby, offers few openings for effective dissent. And for a long time this arrangement has been fortified by the Brahmins’ ability to smother criticism within the broader electorate.

But as the polls show, dissent is there and is not confined to less-educated people. Many graduates are unhappy, but so far only a handful are openly opposed.

Taking a strong stand against racism is a core moral principle, and rightly so. The problem lies in automatically equating any criticism of high migration with racism. All this does is feed the growth lobby and stoke growing discontent among the silenced.

We must be able to debate the future of Australia clearly and publicly. Whispering is not enough.

Katharine Betts is adjunct associate professor of sociology at Swinburne University. The results of the TAPRI survey are at tapri.org.au.