Obviously, McConnell has some ideological ends in mind. And it is rational to argue that he could pursue these ideological ends more effectively with a Republican president, and thus that the benefits of any compromise with Obama are outweighed by the costs entailed by giving Obama a bipartisan achievement and thus increasing his odds of election.
On the other hand, the combination of the American political system and the role of parties creates an important role for social norms that require party leaders to ignore political aims for at least some period of time and consider passing legislation that is mutually acceptable to both parties. McConnell is stripping off even the pretense left by those social norms, creating a situation in which even the most obviously beneficial legislation cannot be passed due to the opposition party's zero-sum interest in worsening conditions. McConnell's strategy calls for blocking even bills that conservatives believe would improve the country. It's not impossible to justify in ideological terms, but it's pretty far from admirable.
Say what you will about the tenets of Liberal Fascism, dude -- at least it's an ethos.