Prejudiced Homosexual Rights Advocate Discriminates Against Polygamists

Here's an opinion piece in support of homosexual marriage in The Age, an Australian publication. The same sort of argumentation Jonathan Wilkinson uses in this editorial could be used to support incestuous marriage, bestiality, or polygamy, for example. But Wilkinson writes at one point:

"If the exclusionary and prejudiced amendments to the Commonwealth Marriage Act were changed to allow marriage between any two persons, a federal civil union scheme could also be created."

Why "any two persons"? Why only two, and why only "persons", if persons are being defined as humans?

Homosexual marriage is just one step that will soon after lead to further steps. In this nation, court cases along the lines of what I've mentioned (polygamy, etc.) are already underway.