The reason they would do this is more than clear. They want to defeat President Obama, and what better way than to screw with the economy. I think we could easily define them as sociopaths.
There is strong evidence to support intentional economic sabotage, some of which is being touted by old school Conservatives themselves. Andrew Sullivan in a piece entitled “Boehner's Economic Terrorism”:
We have a potential catastrophe of national default, an event whose consequences are unknowable but which could quite easily wreck the US and global economies, profoundly damage people's savings, raise interest rates and destroy jobs for a very long time.[…]
Sullivan on the options available to the president:
[…..]It seems to me there are two options the president can take. The first is what you are told to do when a criminal or terrorist holds a gun to your head. You surrender.
The point of economic blackmail is that it works. If you have a scintilla of public responsibility and you hold public office, you cannot allow default. And so you give them everything they want. You announce this while declaring you abhor the package but have to back it for the sake of the national interest in preventing catastrophe. You detail and expose the Republican priorities far more aggressively than in the past. You blame the performance of the economy entirely on them from now on out. And you run on a platform of shared sacrifice - of revenue-enhancing tax reform and tax hikes for millionaires. Then you run against the Republicans as hard as you can.
The second option is to bypass them, invoke the 14th Amendment, and order the Treasury to keep paying its debts because an extraordinarily reckless faction wants to destroy the American economy in order to save it (and pin the subsequent double-dip recession on Obama). Bruce Bartlett outlines the mechanism here. He has some other ideas for coping here.
What does this say about not only the modern GOP, but our system itself?
What you probably cannot do is negotiate with [the] economic equivalent of terrorists. What Cantor and Boehner are doing is essentially letting the world know they have an economic WMD in their possession. And it will go off if you do not give them everything they want, with no negotiation possible. That's the nature of today's GOP. It needs to be destroyed before it can recover.
These people need to be defeated, and in my opinion, charged with something akin to treason.