That usage is pretty standard. The "against" is sort of implied.

I've never heard that usage before, and I was an English major.

It threw me when I read it, as it's one of those instances where the implied meaning is completely opposite to the literal meaning.

argue has two meanings, to disagree and to assert. –verb (used without object) 1. to present reasons for or against a thing.

I agree that it's ambiguous.

To argue is to present an argument. If you argue about something then your stance is unclear. However, if you argue a stance then you are arguing for that stance.

Example:

Tom argued about the war (unclear stance).

Tom argued the war was a bad thing (clear stance, Tom disliked war).

However, there may be a regional usage of 'argue' as 'question' or 'dispute' ("nobody could question/dispute the iphone's success") that I am unaware of.

puffythefish was just arguing the arguer's argument was arguably arguable.

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