He was on with John Mason, whose motion on the subject of same sex marriage caused such controversy earlier in the year.
It was really telling to watch Mason wriggle and squirm and do anything other than give a clear answer when asked whether he believed in equal marriage while Willie was perfectly comfortable discussing it openly.
I thought he was particularly strong on two points, firstly that marriage does not belong exclusively to the church, it belongs to society as a whole, and when he showed the difference between stating a case and making a threat. He had taken the Catholic Church to task last month for overstepping its powers on this.
For me, as you will no doubt be aware, this is about a fundamental issue of freedom - and allowing equal marriage but not forcing it on those religious organisations who don't wish to offer it is the way to give maximum freedom everyone - and I'm glad to see Willie arguing so compellingly for change. He has really gone out there to try to win over hearts and minds on this.
You can watch that part of the programme here.