Except for the fact that he beat them twice, conservative really don't have any reason to hate Obama. "Obamacare" is just the Heritage Foundation health care plan, aka Romneycare, and otherwise, uh, what?
I'm not making the argument that Obama is just like a Republican, just making the point that he really hasn't given them much to work with. They've seized on Obamacare because it's the big legislative accomplishment, but they're mostly incoherent (or lying) about why it makes them so mad. It's just the thing they've chosen to rally behind because they really don't have anything else.
I suppose there's Benghazi!