They can't take a stand on this issue. Half of 'em support Israel, the other half are as rabidly anti-Israel as they are anti-Bush,
Taking a stand or writing about it will split the left-wing right up the middle.
They can't afford that, and they know it. Hence, they are silent.
It is simpler than that. Pacifism is clearly delusional in this situation, and they are pacifists. Anything they could possibly say would be hopelessly stupid or compromise their vapid "principles".