The U.S. is about to make a disastrous blunder in its terrorism policies.

In recent months, a series of savage shootings has drawn attention to the dangers posed by far-right, or white-supremacist, terrorism. Commentators from across the political spectrum have demanded a robust response, and law enforcement agencies are clearly listening. In principle, such a focus on the terroristic far right is an excellent idea.

American debates over terrorism invariably involve a dispute between the left and right over where to focus. Broadly, right-wing thinkers view terrorism as something that comes from outside the country, usually from foreign or international movements, whether communist or Islamist. In contrast, leftists focus on domestic terrorism and white-supremacy movements. If the leftist view is correct, then authorities must reorient their efforts away from foreign threats and focus instead on the far right in all its manifestations. Logically, there is no reason why a government should not fight an even-handed war against both threats. But in practice, focusing on one means virtually ignoring the other. The left/right terrorism debate is thus a zero-sum game.

Much is at stake in these ideological wars. If we conclude that the far right is the chief enemy, then activists will use guilt by association with white supremacy to taint any number of nonviolent conservative causes. This manifests notably in debates over free speech, and with anything connected to the so-called religious right. Labels have consequences.

Hence the regular assertions in left and liberal media that far-right violence is more frequent or severe than Islamist threats. After the terror attack in El Paso, an article in Slate argued in typical fashion, “After this weekend, right-wing terrorists have killed more people on U.S. soil than jihadis have since 9/11. So why is the government’s focus still on Islamic radicalism?”

But conventional statistics offer no worthwhile basis for judging the actual degree of threat posed by particular groups. The whole point of counterterrorism investigation is to prevent and pre-empt attacks, not to clean up after them. Moreover, most counterterrorism is clandestine. Agencies strive not to arrest or try culprits, but rather to turn them and run them as infiltrators within the organization. In that sense, any case that results in a conviction may represent a failure to use that individual convict to undermine an entire terrorist organization.

The question of pre-emption is crucial for understanding the number and lethality of terror attacks. Imagine this hypothetical: In one year, Islamist terrorists plan 10 attacks on the U.S., all hideous acts of mass destruction which between them could kill 5,000 people. Suppose that all are prevented by U.S. authorities, and none even come to the public’s attention. Meanwhile, far-rightists also plan 10 attacks, half of which come to fruition, killing 100 people. If we count actual attacks, then the far right would lead Islamists by five to zero. In terms of fatalities inflicted, they lead by 100. If you did not understand what was happening, you would conclude the far right is much more active and determined, while the Islamist menace is trivial or nonexistent. You would also be totally wrong.

Counting the number of victims killed by a terrorist faction has precisely nothing to do with the potential threat it poses. Rather, a low number of deaths can be interpreted as a statement of the efficacy of counterterrorism intervention. The low number of deaths associated with Islamists in recent years reflects how very difficult it has been for them to operate in face of crushing pressure from U.S. intelligence and law enforcement. Meanwhile, the Islamic State’s propaganda and training networks have been demolished, accounting for the steep decline in Islamist assaults on U.S. soil. If that pressure ever relaxes—and if the Islamic State reconstitutes, for instance in West Africa—then Islamist attacks will again soar.

We regularly see partisans on the left and the right attempt to emphasize the threat of the kind of terrorism they think is serious. They focus entirely on either internal or external menaces and grant no legitimacy to the other side’s point of view.

To see where this can lead, look no further than the late 1990s, when the Oklahoma City bombing led media and politicians to view terrorism entirely in terms of the domestic far right and white supremacists, a stereotype reflected in dozens of films and television programs that followed the bombing. Anyone who suggested Islamist militants were at least as dangerous risked being called racist or Islamophobic. The resulting selective blindness led directly to massive intelligence failures and blunders, the scale of which became evident on the morning of 9/11. I have a grim suspicion that this is what is happening in 2019.

Let’s not go down that road again.