Things I don't understand

There are many such things. One prominent amongst them is Anglicanism. I am, however, a great fan of Rev. on the BBC in which the aforementioned rev recently got into hot water for very nearly blessing a civil union as a result of which he then quietly blessed the civil union. Does anyone know what the problem with an Anglican priest marrying two people of the same sex should be for an Anglican? I'm not really sure. They changed the matter of their sacrament of ordination in order to be gender neutral. Why not just change the matter of their sacrament of marriage for the same reason? Most of them seem to be in favour of gay marriage, why not just take the opportunity?