The Volokh Conspiracy gets it right on Obama's attacks on NRO's Stanley Kurtz.
Barack Obama and his campaign have denounced Ayers’s actions and at least one of Ayers’s statements, but I think that neither Obama nor his campaign has ever denounced Ayers himself. As with the first Reverend Wright speech, this is no accident. Obama usually takes the “Christian” position: hate the sin, love the sinner.
Kurtz, unlike Ayers, is denounced in the most vicious and uncivil terms (there is a lot more than I quoted). If Obama or his campaign had ever denounced Ayers with the fervor that his campaign has now used in denouncing Kurtz, Obama wouldn’t be having trouble on his connection to Ayers. And I’m not suggesting that Obama should have denounced Ayers. I am just noting the grossly disproportionate responses of the Obama campaign to their differing offenses and the Obama campaign’s direct attack on Kurtz’s character, not just what he's done or said – including very explicitly using arguments of guilt by association against Kurtz (which of course are being used against Obama, despite the protestations to the contrary of his critics).
You know a man by his friends, and his enemies.