JOSEPH NOCERA: Boy, that Keystone Pipeline decision was a stinker, wasn’t it? But it’s not Obama’s fault. It’s America’s. “I realize that President Obama rejected Keystone because, politically, he had no choice. My guess is that, in his centrist heart of hearts, the president wanted to approve it. But to give the go-ahead before the election was to risk losing the support of the environmentalists who make up an important part of his base. . . . Surely, though, what the Keystone decision really represents is the way our poisoned politics damages the country.”