In the Democratic debate from Des Moines on NPR this afternoon, former Senator Mike Gravel said that Iran's support for terrorism was both justified and understandable. Gravel said that such support is appropriate because voters in the region have elected members of Hamas and Hezbollah and because Israel is threatening Palestinians. Gravel has always been a marginal candidate. (He said in the same debate that Iran "has never been a problem and never will be.") But here is what's interesting. Not one of the other Democrats participating in the debate (everyone other than Bill Richardson) objected to his justification of Iran supporting Hamas and Hezbollah. It was a troubling silence.