"But we must also recognise that there is a sense in which homosexual partnerships are not the same as heterosexual ones and this difference should also be celebrated."

The crux of this bullsh!t argument.

Name them, Ian.

What are these critical, defining differences?

Can't be kids, because many marriages are childless - and always intended to be childless, eg marriages post menopause.

What's the difference? What's the thread that draws all heterosexual marriages together that cannot be present if the couple is homosexual?

You haven't got an answer to that. Because there isn't one.

Jeremy Sear,
It is a husband having vaginal sex with his wife. The vagina was specifically and exclusively designed for heterosexual sex. The vagina has no other function. That is what the term marriage means. The joining together of a man and woman in an exclusive sexual union. Two males improvise by using the anus which was never designed for sex and has another purpose and that is to excrete faeces. This is not a celebration but a perverted act