As faculty members whose research was affected severely by a 2001 firebomb attack by the Earth Liberation Front (ELF), we object to the assertion in your Editorial 'Unwise branding' (Nature 447, 353; doi:10.1038/447353a 2007) that charging ELF arsonists with terrorism could amount to erecting an “unbreachable wall” to dialogue between them and scientists.

The ELF and its sister the Animal Liberation Front (ALF) use violence against civilian targets to further a political viewpoint: this is the definition of terrorism. Calling the ELF and ALF terrorist organizations is a simple statement of fact. There is no need to mince words in a vain effort to placate groups whose members, through a dangerous combination of wilful ignorance and willingness to enforce their world view 'by any means necessary', eschew reason in favour of senseless violence.

Some ELF and ALF apologists believe that 'property damage' (including destruction of research buildings at universities) does not qualify as terrorism. Perhaps the ELF statement from which we quote below will give those apologists a glimpse of the perspective shared by those of us whose names and addresses have been posted on ELF or ALF websites (which link to instructions on firebomb construction and deployment). After the firebombing of a US Forest Service laboratory in Pennsylvania in 2002, the ELF declared: “segments of this global revolutionary movement are no longer limiting their revolutionary potential by adhering to a flawed, inconsistent 'non-violent' ideology. While innocent life will never be harmed in any action we undertake, where it is necessary, we will no longer hesitate to pick up the gun to implement justice, and provide the needed protection for our planet that decades of legal battles, pleading, protest, and economic sabotage have failed so drastically to achieve.”

Simply put, ELF and ALF members are anti-science, anti-intellectual, anti-human fundamentalists — certain that they have privileged access to some universal truth, deaf to alternative arguments, blind to evidence and determined to intimidate those who disagree with them. They are self-righteous in firebombing the very institutions (such as ours) that sponsor research and open discourse to understand and improve the state of the Earth for all its inhabitants. ELF and ALF terrorists have built the wall of naive, intolerant fundamentalism between themselves and us — only they can breach it. Rational people are, and always have been, waiting on the other side in the hope of receiving some form of communication other than a bomb or a bullet.