Groans and heckling greeted Liberal Senator Cory Bernardi each time he raised the rights of children to be allowed to know their mother and father.

Loud applause greeted Senator Penny Wong each time she made a point supporting same-sex marriage.

In what was the hottest ticket in town today at Canberra's National Press Club, the atmosphere felt more like ABC1's Q & A program as the two debated changing the definition of marriage.

With a cross-party bill to be introduced into Parliament in two week's time, today's press club debate was a sell-out.

The pair jousted over rights of children and freedom of speech and conscience.

While Senator Wong rightly points out that some same-sex couples already have children, she does not engage with the ethics of surrogacy and anonymous sperm donation, both seen as necessary for same-sex family formation. Both are ethically fraught.

In fact, Labor voted at its National Conference at the weekend to ensure that if it is in government same-sex couples have equal access to assisted reproductive technology.

This of course means guaranteeing that children miss out and that donor parents also miss out on relationship with their biological children.

It was clear the crowd at the press club want no discussion about children in Australia's debate to abolish husband and wife from the Marriage Act.

Senator Wong made it clear that mothers and fathers are not necessary to a child as love and stability will do.

This of course is not the lived experience of the victims of forced adoption who were apologised to by Prime Minister Gillard despite the fact most of them had loving and stable families.

The working journalists who asked the questions today directed most to Senator Bernardi. They are perplexed at why anyone would oppose same-sex marriage and why a mother and father mattered to a child.

Our political and media class have lost their capacity to reason.

On a positive note, even advocates for change such as Senator Wong are now beginning to acknowledge that there are consequences to freedom of conscience if marriage is changed in law.

Senator Wong said suppliers to the wedding industry would not be forced to violate their conscience by being forced participate in weddings they did not believe were true marriages.

"Our existing system of anti-discrimination laws contain exemptions," Senator Wong told the press club.

Sadly she is wrong about this.

Her Labor colleague in the Australian Capital Territory, Simon Corbell, wrote to ACL to say these exemptions would not apply to wedding service providers.

It is disappointing that there is so much ignorance in this debate. The discussion in the public discourse has been one way for the past several years.

We are only just starting to have a more mature debate but most people will not have seen the full suite of arguments put forward by Senator Bernardi today.

They will see the edited highlight on the news.

More time and discussion is obviously needed.

The same-sex political lobby should not be allowed to dismiss discussion about children and freedom in a bid to rush same-sex marriage through the parliament.

Today's debate giving a platform to someone like Senator Bernardi is only just the beginning of the more balanced discussion that is necessary.