Many liberals respond to the Export-Import Bank fight by shrugging, rolling their eyes, and saying "what an odd fight to pick." This relieves of them of having to either (a) defend corporate welfare, or (b) side with Tea Partiers over President Obama.
But Ezra Klein at Vox.com seems to get it:
[T]he fight over the Ex-Im Bank might prove, in the long sweep of American politics, to be something of a political turning point. It has become the top priority of a dedicated group of conservative policy entrepreneurs who want to see the Republican Party hack away at the ties between big government and big business. And the Ex-Im Bank might prove to be something their movement badly needs but hasn't scored until now: a win. ...
This is key to why the fight against "crony capitalism' has become so important to reform conservatives: many business interests profit from current government policies, and so a necessary predicate of reform conservatism is for conservatives to get comfortable fighting big businesses that partner with the state.