Original source article. Cockburn's article's actually about Rahm Emanuel, and his digression about Miliband is about how in the end of the day the blame for the criminality of such depraved ghouls like Emanuel lies with the goody-goody "progressive liberal" types like Obama.

I don't quite understand what you're getting at in your comment? Cockburn's rhetoric is definitely aggressively combative, but I definitely don't think that he's being smug or insincere or manipulative ar all. In fact, I honestly think that he's actually extremely close to being purely sincere and moralistic. The key idea is that he sees the actually existing suffering and injustice around the world and feels justifiably angry at that, and he's pointing that fury at the right people and institutions, i.e., those most responsible for creating and perpetuating unjust socioeconomic systems of capitalist/imperialist exploitation. He's not at all saying that you should act like a jerk towards everyone around yourself without rhyme or reason; he's talking about there being a class war going on, and the need for principled leftists to recognise their enemies and adopt the right attitude towards them in such a situation.