Further evidence of the intolerance of the leading voices in the same-sex marriage debate will be on display again at this weekend’s Australian Labor Party National Conference in Melbourne.

At its last conference in 2011, Labor changed its party policy to support redefining marriage in law. It was a terrible blow to have one of the two major political parties capitulate.

However, at that time, Labor made an important concession. Normally conscience votes on both sides of politics are reserved for life or death matters such as abortion or euthanasia.

But in this case, after tense backroom negotiations, Labor decided to depart from this political rule of thumb and allow its parliamentarians a conscience vote.

Under Labor’s party rules, parliamentarians who vote against party policy are automatically expelled. (The Liberal’s don’t expel in these circumstances but a politician’s career prospects can be curtailed.)

At the time, Labor did not want the prospect of booting out caucus members who did not support same-sex marriage.

Fast-forward to now and the tables have turned.

A motion will be put to the conference this weekend, which if passed, will bind Labor’s parliamentary team to supporting a same-sex marriage bill.

This will put a number of members and senators in a difficult position should the issue come up again in the Parliament.

What is worrying is the intolerance of such a move.

If same-sex marriage and the ideology it carries must be supported by politicians, what message does that send to the rest of the population?

Millions of us will never support a definition of marriage that requires a children to miss out on their mother or father.

Christian schools will always want to teach Jesus’ definition of marriage in defiance of the state’s definition.

To have a major political party entrench in its policy platform the idea that there is no room for dissent, is chilling and shows just how intolerant those driving the political debate are.

I’ll be at the ALP conference, principally to chair a symposium on persecuted religious minorities.

But I will be watching Labor’s debate on marriage with interest (and tweeting @LyleShelton). If a major political party decides to be intolerant with its own members on this, it is sure to be intolerant with the nation when it is again in government.