Illogical? The only illogical thing is to NOT be able to see polyamory as an extension to the 'rights' principle being espoused to justify SSM.
I think the word 'equal' is important if the rights thing is going to be discussed as a principle.
Equal rights.
All Australian adults have equal rights regarding
1/ choosing their religion
2/ practicing Polygamy
3/ choosing whether or not to have children
4/ driving while drunk
5/ getting married..............hang on......
All I'm saying is that the argument of equal rights can probably be applied to SSM quite successfully but it can't be applied to Polygamy because equal rights already exist on that matter. If they wanted to push for Polygamy the argument would have to be something else.