LEIGH SALES, PRESENTER: Advocates of same-sex marriage warn that the postal survey could lead a vitriolic campaign of hate.

But opponents say that, frequently, they're the ones being victimised.

Tonight 7.30 meets people from the 'no' camp who say they've been trolled and abused, online and in real life, for their belief marriage is between a man and a woman.

Julia Holman reports.

(Mark Poidevin enters kitchen, where Ben Rogers is

BEN ROGERS: Hey, Markie. How was work this morning?

MARK POIDEVIN: Yeah, it was interesting today.

BEN ROGERS: Would you like a cup of tea?

MARK POIDEVIN: Yeah. It sounds great.

BEN ROGERS: Enjoy. Cheers.

MARK POIDEVIN: We met 15 years ago on gay.com and it was love at first sight. We've been through our ups and downs, like anyone else, I suppose. We've had moments of up and down.

BEN ROGERS: Yeah.

MARK POIDEVIN: But you know, I love him dearly and there's nobody else I'd rather spend my life with than him. So...

BEN ROGERS: Yeah. That's true. And I feel the same. So, yeah.

MARK: Might go out and sit with the dogs.

JULIA HOLMAN, REPORTER: Ben Rodgers and Mark Poidevin consider themselves a typical couple. But their views on same-sex marriage aren't what you'd typically expect.

MARK POIDEVIN: I used to be a supporter of same-sex marriage. I mean, I proposed to Ben five years ago.

BEN ROGERS: I just explained to him. I said, "I don't think it's my cup of tea," you know. It's not something that I'd ever envisioned.

Like, when I first came out, I think one of the consequences of coming out was giving up, you know, marriage and children and things like that.

MARK POIDEVIN: If we make one exception for one community - that being the same-sex couples - where does it stop? Do we then see other cultures being allowed to have multiple marriages? Do we allow, see the age of consent being lowered for another group of minorities? That is my concern of where it would lead.

JULIA HOLMAN: Mark, who is a committed Catholic, wanted to take part in the public debate on same-sex marriage.

(Audio recording of talkback conversation, 96.5 Wave FM)

MARK POIDEVIN: Well, my partner and I actually are a gay couple and we'll be voting 'no'.

TRAVIS WINKS, PRESENTER: What? Hang on a second. Hold the phone.

MELISSA GREIG, PRESENTER: No against marriage equality? Or...

TRAVIS WINKS: You're voting 'no'?

MARK POIDEVIN: No against same-sex marriage.

(Recording ends)

JULIA HOLMAN: But arguing 'no' has come at a price.

MARK POIDEVIN: The campaign has gotten nasty on both sides and I think the comments that I hear is: "You're a homophobe if you don't support gay marriage."

Well, I'm a gay person here that's coming out and saying: well, no, it's not. It's your right to have a view: your right to have a view either way. And I think people should be respected for each way. You're not intolerant if you don't support a view.

(Footage of Karina Okotel and her husband with their daughter, Hannah, in a park)

KARINA OKOTEL, VICE-PRESIDENT, LIBERAL PARTY: For me: you know, in terms of racism, you wear the colour of your skin on the outside. So it's something you can't hide. But when you have a particular view - a political view or whatever - and you're ridiculed for it, it is something that you can withdraw from or you can not voice.

And I think what is happening is that people who have those views are being shamed into silence. And that's something that is really sad.

(Karina Okotel takes a smart phone photo of her daughter)

KARINA OKOTEL: Hannah! Hannah, smile. Look here.

JULIA HOLMAN: Karina Okotel is a lawyer and vice-president of the Liberal Party. She says she's faced a backlash for publicly expressing her opposition to same-sex marriage.

KARINA OKOTEL: I think it's mainly the 'yes' side, I would say, that do try to shut down debate or do try to paint people who are not in favour of same-sex marriage as being homophobic or being out of touch or ridiculing them as well.

It is important to think through what those flow-on ramifications will be, in terms of the impact on free speech, in terms of the impact on freedom of religion and association.

JULIA HOLMAN: From the very beginning, there have been concerns that this debate would descend into mud-slinging and that the LGBTI community would come off second-best.

PENNY WONG, LEADER OF THE OPPOSITION IN THE SENATE: I and many others oppose this bill because we already know what hate speech feels like. We oppose this bill because we do not want our families and our children publicly denigrated.

ANDREW LEIGH, SHADOW ASSISTANT TREASURER (Lateline, 10 Aug.): It will be divisive. It will hurt families.

JIM CHALMERS, LABOR MP FOR RANKIN (10 Aug.): As this plebiscite goes on, there is the capacity for people to make hateful remarks.

BILL SHORTEN, OPPOSITION LEADER (8 Aug.): Why is the Prime Minister making Australians pay $122 million to give licence to this vile rubbish?

JULIA HOLMAN: Now the 'no' case is arguing they're the ones copping the heat.

KARINA OKOTEL: At the moment, I think that people who haven't really entered into the debate: they haven't done so because they are scared about backlash; that they are scared their views might be taken out of context or, just because they have a view that opposes same-sex marriage, they might be seen as hate-filled, homophobic, bigoted; and that is something that nobody wants to be called.

TOM SWITZER, CONSERVATIVE BROADCASTER: Several serious subjects cannot be debated openly now without eliciting a hostile, even hysterical response.

And unfortunately, I think same-sex marriage is one of those issues. Many of the same-sex marriage zealots in the debate are increasingly intolerant of those who hold a different view.

TIERNAN BRADY, DIRECTOR, EQUALITY CAMPAIGN: No matter what one's opinion on in any issue, no-one should ever be bullied. And of course, there's probably no greater group of people than lesbian and gay people who understand what it's like to be bullied.

JULIA HOLMAN: Tiernan Brady is urging both sides to engage in a respectful conversation.

TIERNAN BRADY: I get the Twitter trolls and I get the Facebook trolls. I get letters written to me as well, that range from slightly disrespectful to, you know, utterly outrageous. But you have just got to keep your eye on the bigger picture.

JULIA HOLMAN: Tomorrow the High Court will hear two challenges against the postal survey, with a decision expected by the end of the week. But already the debate is changing views.

TOM SWITZER: My views on same-sex marriage have evolved. I now support same-sex marriage.

But if the zealots in the debate continue to use this issue as a way of creating a new, stifling orthodoxy that tolerates no dissent and demonises good and decent people who are opposed to same-sex marriage, I, like many other ordinary people, will switch my vote.

MARK POIDEVIN: This could be the Brexit or Trump moment for Australia, where people: the polls are saying one thing but you go to the ballot box and people are clearly in another mind, going to vote another way.

BEN ROGERS (to pet dog): Rexie, don't be a snob.

JULIA HOLMAN: Even if same-sex marriage is legalised, Mark and Ben won't be walking down the aisle.

JULIA HOLMAN: If it's yes, we'll be like: OK, then, well, congratulations. Everyone can get married. But we personally will not be getting married. We'll stand by our commitment to each other. You know, we don't need marriage in our lives. Definitely not.