What we need - and we aren't seeing - is a firm stand by moderates against religious extremism. . . .
The closest parallel I can think of to current American politics is Israel. There was a time, not that long ago, when moderate Israelis downplayed the rise of religious extremists. But no more: extremists have already killed one prime minister, and everyone realizes that Ariel Sharon is at risk.
America isn't yet a place where liberal politicians, and even conservatives who aren't sufficiently hard-line, fear assassination. But unless moderates take a stand against the growing power of domestic extremists, it can happen here.
Krugman's warning reminds me of a similar warning that James Davidson Hunter gave in his book, Before the Shooting Begins. The casual use of military metaphors and talking about conscientious differences of judgment and opinion as "culture wars" can easily incite some minds to respond with literal violence.