Yglesias tries to distinguish between people who are worried about the declining dollar because they are cranks, and people who are worried about the declining dollar because it is a good stick with which to bash Barack Obama:
Now if you know someone who spent all of 2007 and the beginning of 2008 lambasting conservative economic policies for destroying the value of the dollar, and then who felt that good things were happening to the economy during the fall and winter of 2008, as reflected in the rise of the dollar, then you know someone who's a crazy crank. But he's a crazy crank who's earned the right to complain about Obama! But if you know someone who never mentioned the falling dollar in 2007, and never mentions today that the Obama-era "plummet" merely reflects a reversion to where things were before the financial panic, then you know a partisan crank.
As you all know, I do not much worry about the "weak dollar". But while Yglesias' rule is correct, it is not very useful, because I am afraid that the dollar cranks now were mostly dollar cranks then. Mr Yglesias wouldn't necessarily have much way of knowing, because they probably didn't spend a lot of time in his comments section, and I doubt he's an afficionado of conservative financial gurus. But trust me: they were going strong during the Bush administration. There is simply a very substantial overlap between the groups of people who hate Barack Obama, and the groups of people who agonize over the relative value of the dollar.
It's like opposition to the war. It's entirely true that the war became an excellent stick with which to bash George Bush. But that was not actually the reason that most of the people who were against the war happened to also be people who hated George Bush. Rather, the more reflexively pacifist you are, the more likely you are to be a member of the Democratic Party, or some group to the left of the Democratic Party. The correspondence is not 1:1. But it's close.