As we debate what kind of rhetoric is and isn't objectionable, it would help if we could make some specific distinctions and keep some important things in mind. To that end:
Every gun metaphor is not created equal. Military metaphors infuse our talk about politics; the only thing that comes close is sports. The word "campaign" only relatively recently began to be used to refer to politics; its original use referred to military endeavors. But there is a difference between using metaphors that invoke violence ("We're going to fight this battle to the end!") and using rhetoric that invokes violence specifically directed at your opponents (like this), or even speaks literally of people arming to take on your opponents or the government (like Sharron Angle's infamous discussion of "Second Amendment remedies" to not getting the result you want at the ballot box). One is perfectly ordinary; the other ought to be condemned.
The fact that someone criticizes your rhetoric doesn't mean they're "blaming" you for the Arizona shooting. Right now, Sarah Palin's defenders are angrily denouncing people for "blaming" her for the shooting, because people have pointed to her now famous crosshair map of candidates she was targeting for defeat in 2010, including Gabrielle Giffords. But no one is saying this guy committed his massacre because he looked at this map. What people are saying is that this kind of thing goes too far. Certain things contribute to an atmosphere in which violence becomes more likely; criticizing those things doesn't mean you've said that in the absence of one particular statement or Web posting this event wouldn't have occurred.
If you think your rhetoric is above reproach, you have an obligation to defend it on its merits. Naturally, many on the right are going to attempt to turn the criticism of them around on the left: See how they're playing politics! But if you think it's perfectly fine for you to say what you've been saying, explain why. Attacking the motives of those criticizing you doesn't qualify.
Asking you to tone it down is not censorship. Over at Slate, Jack Shafer defends inflammatory political speech by saying, in part, that "any call to cool 'inflammatory' speech is a call to police all speech." As someone who has spent many years tangling with conservatives over their rhetoric, I've heard this argument a million times. When you criticize some talk-show host for something he said, he inevitably responds, "You can't censor me!" The First Amendment guarantees your freedom to say whatever idiotic thing you want, but it doesn't keep me from calling you out for it. No one is talking about throwing anyone in jail for extreme rhetoric, but we are talking about whether people should be condemned for certain kinds of rhetoric.
The rhetoric of violence is not the only kind of rhetoric that encourages violence. The apocalyptic rhetoric we've seen from some on the right, most notably Glenn Beck, should be part of this discussion too. When Beck portrays Barack Obama as the head of a socialist/communist/Nazi conspiracy whose goal is the literal destruction of America, he is implicitly encouraging violence. If that really were the nature of the administration, and our liberty really were on the verge of being snuffed out, violence would be justified.
If you're going to say "Liberals do it too" then you ought to provide some evidence. No one disputes that there has been a tide of extreme and violent rhetoric from some quarters of the right in the last couple of years. But any journalist who characterizes this as a bipartisan problem ought to be able to show examples, from people equal in prominence to those on the right (i.e. members of Congress, incredibly popular radio hosts, etc.) who have said equally violent and incendiary things. "Harry Reid once called George W. Bush a liar" doesn't qualify, nor does a nasty comment some anonymous person once left on a blog.
-- Paul Waldman