Slate‘s Jack Shafer says it so that I don’t have to:
For as long as I’ve been alive, crosshairs and bull’s-eyes have been an accepted part of the graphical lexicon when it comes to political debates. Such “inflammatory” words as targeting, attacking, destroying, blasting, crushing, burying, knee-capping, and others have similarly guided political thought and action. Not once have the use of these images or words tempted me or anybody else I know to kill. I’ve listened to, read—and even written!—vicious attacks on government without reaching for my gun. I’ve even gotten angry, for goodness’ sake, without coming close to assassinating a politician or a judge.
The only thing I’ll add is that government officials command such vast power — power to bankrupt, imprison, maim and, yes, kill — that refraining from using “vitriol” (as Pima County’s Sheriff Clarence Dupnik puts it) in criticizing people who seek to wield that power borders on the irresponsible.
Update: Liberranter correctly points out that this is an appropriate place for John Green’s (the father of slain Christina Green) moving call to refrain from using this incident as an excuse for more restrictions on our freedom.