The United States is still in shock today after an assassin targeted a political meeting in Arizona on Saturday. Congresswoman Gabrielle Giffords, remarkably, survived being shot in the head at close range, but six others — including a federal judge and a nine-year-old girl — were not so fortunate; another ten or so people were injured.

No-one wants to be seen to be exploiting tragedy for political gain, and it is especially important to avoid the temptation of tagging one’s opponents as potential terrorists. Political leaders from both sides have condemned the attack in the clearest of terms, and there is no reason at all to doubt their sincerity.

Nonetheless, violence does not happen in a vacuum, and it is right to point to the escalating intensity of America’s political discourse as a likely factor in this sort of incident. Tony Blair famously promised to be “Tough on crime, tough on the causes of crime”, and the enquiry into causes needs to go beyond this particular crazed gunman and on to the rhetorical climate that fosters such craziness.

Nor will it do to try to be even-handed and suggest that “both sides are to blame”. Of course there are extremists on both sides, but the American right has given mainstream acceptance to extremists and extreme rhetoric in a way that the left simply has not.

Doubters could perhaps start with the carefully documented chronolog of “insurrectionist” incidents compiled by the Coalition to Stop Gun Violence. It shows the eerie correspondence between what accepted Republican politicians and opinion leaders have been saying and the actions of nutters who have taken some of those ideas to their logical conclusion.

The point is not — contrary to what some gun control advocates maintain — that there is anything intrinsically wrong with the notion that private gun ownership represents an ultimate safeguard against oppression. (Those who think this is a crazy idea might like to read about Switzerland). The point is that the rhetoric of the Obama-haters is so wildly out of proportion to any of his real or alleged misdeeds.

On any rational accounting, the US is further from tyranny now than it was three years ago, when Dick Cheney was still plotting the overthrow of all constitutional restraints on executive power. But there is a basic asymmetry in the way the two sides of politics have reacted to being out of power (and of course Bush and Cheney were white, which in America still makes a difference).

Either the firebrands of the right are utterly unscrupulous, exciting their voter base with terminology that they must know is completely inapplicable, or they have themselves lost touch with reality and have no idea what tyranny and oppression really look like.

Whichever it is, it has taken America into dark and dangerous territory.

And the media have been enablers in the process, treating incitement as if it were just business as usual. In a widely re-tweeted comment, Michael Moore said “If a Detroit Muslim put a map on the web w/crosshairs on 20 pols, then 1 of them got shot, where would he b sitting right now? Just asking.”

Although of course they have been subject to criticism, it is hard to see that Sarah Palin and others have been made to pay any political price for their incendiary rhetoric. That may now change, and the country’s revulsion at the murders in Arizona may shift sentiment decisively against them.

But with so many people having so much invested in the denial of reality, that shift will not come easy.