The "currency manipulator" question made a lot of sense in 2000 or 2004 or 2008. It doesn't make much sense in 2012. But the political conversation on this issue, as so often happens, hasn't quite caught up to the facts.
What the GDP-relative figures should tell us is that China's behavior, while of a much larger scale due to the size of its economy, is not all that different from what developed democracies like Denmark or Israel are doing as well. That doesn't make it okay, and Gagnon is clear that this behavior gives manipulators an unfair advantage, but it does put the singling out of China into perspective.