As per my post quoting Sartre on antisemitism, here are some more thoughts:

I think Sartre's novelty is the acknowledgement that Antisemitism is not a disease that Jews can cure. Their very existence is a contributing factor to its persistence. Those who aren't Jewish or antisemites ought to be able to recognize and deal with it.

But I've noticed that those who are not antisemites tend to keep their silence when people like them (I mean of similar ethnic identity and political affinities) utter unforgivable antisemitic statements. They tend to be forgiving about these lapses, make excuses, as though it was not really meant, as though it was somehow provoked. When they can't excuse, they ignore and continue their friendship with the antisemite as though no harm was done to the fabric of good humanity, or to Jews. If they are particularly fond of that antisemite, then they somehow manage to rationalize the whole thing, stand it on its head. The antisemite is then presented as a victim, persecuted, poor thing, by constant reminders of his vile statements.

This denouement, which I witnessed on a few occasions, is an ironic travesty of Sartre's insight, in which the friends of antisemites bring to their defense too much of the passion and the perseverance their critics (Jews) use to try and expose them for what they are.

By some fluke, Normblog has posted this short-short story today in which the following paragraph appears, describing the phenomenon of the "friend":

"His friends encourage him. If not openly, they always listen politely, and comment on his grasp, or if they never comment on his grasp at least they never contradict him. Or at least not openly, or if they do disagree openly they never take the battle seriously. Never back themselves up or keep the argument going. Never really take part, to be honest."