Consider the events of 2006.

In May, John Howard's government introduced tough immigration laws that would excise mainland Australia from the Migration Act for asylum seekers. For the first time, all who came by boat would be sent offshore for processing, rather than just those unlucky enough to be sent to Nauru or Manus Island.

It was a wildly controversial move, and sparked fierce debate about whether Australia could protect refugees' rights in island detention centres on foreign soil.

After heated debates, three of Howard's backbenchers, Broadbent, Judi Moylan and Petro Georgiou, defied their government and crossed the floor to vote with Labor against the legislation. Fellow Liberal MP Bruce Baird openly spoke out against the bill, but abstained.

Echoing the Midnight Oil lyric, Broadbent told Parliament: ''If I am to die politically because of my stance on this bill, it is better to die on my feet, than to live on my knees.''

The laws passed the lower house, but the stand of the moderates ensured it was Howard's laws that would die on their feet. On August 14, Howard withdrew his legislation when Liberal senator Judith Troeth - who had led Coalition dissent - threatened to cross the floor to vote against it.

The laws that today send all asylum seekers to offshore processing were introduced under Labor in 2012, which went further than Howard's proposals did.

Labor, ostensibly concerned about asylum seekers' deaths at sea, excised the mainland from the Migration Act, sent all asylum seekers offshore for processing and ensured that no one who came to Australia by boat would ever be settled here.

Last week, one asylum seeker sent to Papua New Guinea's Manus Island for processing was killed after a fracas involving asylum seekers, PNG security forces and PNG police. Another 62 were injured, nine of them seriously, including one man who was shot. So far, no one from the government ranks has spoken out about the hardline policy that sent them there.

Notably absent from the debate in recent months have been the Liberal ''wets'', or social moderates, who so regularly spoke out under the Howard government against mandatory detention and offshore processing.

Broadbent, the sole remaining member of that group of moderates, told Fairfax that ''anybody would be distressed'' by what had transpired on Manus Island.

But he said: ''Both sides of the Parliament have determined that [Manus Island] is a deterrent, so both sides of the Parliament have to wear the consequences of their decisions.''

Broadbent, who with Moylan voted against Labor's 2012 laws, said since the major parties struck their consensus on a hardline approach to asylum seeker policy, there was little place for internal dissent on the issue.

''I'm not silent,'' he said. ''There may be only one left, but I'm not silent. The government knows where I stand. I don't have to speak for them to know, and I don't want to be seen to be using the plight of genuine refugees for my own self-aggrandisement. I've never done that, and I'll never do it.''

Moylan and Georgiou declined to speak to Fairfax, and Baird did not respond before deadline.

With the sole remaining member of the group reluctant to speak out publicly against the policy, what has come of the Liberal Party's famed ''broad church'' under Tony Abbott?

''These things ebb and flow,'' Broadbent says. ''There'll be people that come through into the future that have different views, but at this time, whilst their policies are seen to be hugely successful, there isn't a place for the dissent, nor legislation for the dissent - because the Labor government moved them all. The previous government did all Howard's work.''

Former prime minister Malcolm Fraser, however, has little sympathy for MPs who do not speak out on matters of conscience.

Of Broadbent's reticence to speak out against events on Manus, Fraser says: ''Well, he doesn't therefore think the principle is worth supporting.''

Fraser, who quit his own party in 2010 over its treatment of asylum seekers, despairs of the bipartisanship that has emerged on this topic. He says political leaders have lost perspective on the scale of the problem.

''Australia on this subject is almost like a boxer who's punch drunk,'' he says. ''He's been hit on the head too often and he doesn't really know what's happening. We no longer have the right in any international forum to advance the cause of human rights. Imagine now we go and argue in China for human rights in Tibet, or something like that.''

So is it the party's changing culture, different preselection rules, or simply the strong control of the leadership group over people speaking out that's led to the apparent demise of the party's vocal moderate contingent?

One Liberal insider says timing is everything. ''With the bipartisanship that's sprung up, there's little point putting your head up on this. It's important that people pick their time. Right now it'll be very difficult to have an impact.''

On asylum seekers at least, political scientist Nick Economou believes the electorate has moved on. ''I just don't think there'd be a critical mass of people in the Liberal Party who'd be either willing or inclined to criticise the government's approach, and they're probably reflecting the attitude of the electorates that put them there.''

So does he think the Liberal Party's ''broad church'' has changed?

''No, I think the party's got a diversity of opinion on a range of things, I just think this is an issue that people who've joined the Liberal Party and got preselection, particularly in the outer suburbs, and the people who vote for them are of a like mind on - they want those borders protected.

''This is an issue that's really of controversy for a very small section of the Australian community … I just don't think this is an issue that's resonating with ordinary voters; I think they're more interested in domestic economic matters.''

But Fraser rejects the notion that the Liberal Party remains representative of a range of liberal philosophical views. ''No,'' he says flatly. ''It hasn't been a broad church for a long while.''

For Fraser, the writing was on the wall during the 1980s tussles between the moderates (the wets) and the conservatives (the dries), particularly in John Howard's pursuit of Fraser's ally Ian McPhee, whom he sacked as communications minister in 1987. McPhee later defied Howard and crossed the floor to support Bob Hawke's motion that race and ethnicity should never be a criteria for migration to Australia. He lost preselection the following year.

Says Fraser: ''If there were a moderate - in philosophical terms, a liberal party - emerging again in Australia, I think people would flock to it from the Liberal Party and the Labor Party in their hundreds of thousands.

''And in my book, that would be easier than changing the Liberal Party to that which it used to be.''

Last week, Troeth spoke to year 11 and 12 schoolgirls and was asked about Australia's treatment of asylum seekers. She told them, ''Regardless of the feelings of your electorate, you must still be a human being.''

She tells Fairfax: ''I don't see how anyone could be devoid of compassion on this.

''Particularly in the lead-up to the last election, it was a race to the bottom between the two parties as to who could put forward the most punitive policy, and I find that very shameful.''

But she allows that it is difficult for the few remaining Coalition MPs with dissenting views to make a difference.

''I think the gradual retirement from Parliament of people who were prepared to speak out about it, and the move into government, and the emphasis on 'everybody has to be a team player' … has made it hard when there's such emphasis on toeing the line,'' she says.

''If you do speak out, it's certainly a career marker.

''And I just think people are not willing to jeopardise their future career for an issue that isn't in your face here in the electorate. It's not like employment or jobs or education rates here in Australia, it's for many people something that's happening far, far away in another place.''

Since the election, the only MP to speak out publicly against their government is Victorian MP Sharman Stone, who castigated Abbott's refusal to financially support food processor SPC Ardmona in her electorate.

Fraser hopes that, in time, more MPs from the Coalition ranks will be prepared to speak out about asylum seekers and other social issues - even if it comes at a personal cost.

''You have to believe that, and I believe that, and I want to live long enough to see it, which might make me a very ancient person before I depart this world. But you have to be optimistic.''