Overheated political rhetoric is a long American tradition, and Republicans often engage in it, too.

But at a time in human history when actual terrorists are beheading Americans and filming the carnage — and calling on extremists to murder Americans everywhere in the world, such rhetoric seems not only out of place but uniquely offensive. We seem to have arrived, to paraphrase writer Francis Fukuyama, at the end of civil rhetoric. When one of the highest ranking members of the Democratic Party is willing to compare her political opponents to wife beaters, and another is unwilling to distinguish them from murderous enemies who behead our own citizens, how much more shocking can the rhetoric get? Where else can we possibly go?…

It’s also true that Democrats are under pressure to rev up what appears to be a lethargic electorate or face defeat at the polls in November. It’s unfortunate that we’ve come to accept the idea that voters can only be motivated by fear and anger toward their political opponents. But here’s another thought: Maybe Democratic leaders aren’t finding success in expanding their liberal base because fair-minded Americans don’t easily gravitate to a political party led by people whose default election tactic is to demonize its opponents.