There are few more entrenched areas of debate than climate change. A blogpost by Dana Nuccitelli on January 21, “Matt Ridley wants to gamble the earth’s future because he won’t learn from the past”, garnered 514 comments. The post criticised Lord Ridley’s views as expressed in an article in the Times.

The opening paragraph said: “Have you ever watched a zombie movie and wondered if the protagonists will grow physically tired from having to repeatedly kill zombies that inevitably rise once again from the dead? That’s how people often feel when confronted with climate change myths that were debunked years ago. These myths never seem to stay dead, inevitably being revived by climate contrarians no matter how conclusively and repeatedly they’ve been debunked.” The blogpost used the zombie analogy to discuss Lord Ridley’s views, illustrated by a photograph taken at a festival of someone carrying a dummy zombie head.

Among the comments were two from “Bluecloud”, which elicited the following complaint from Lord Ridley: “Beneath the article appeared the following comment from ‘Bluecloud’: ‘Should that not be Ridley’s severed head in the photo?’ ‘Bluecloud’ was challenged by another commenter with: ‘Do you recommend that for all people that have a different world view than you?’ ‘Bluecloud’ replied: ‘We would actually solve a great deal of the world’s problems by chopping off everyone’s heads.

‘Why are you deniers so touchy? Mere calls for a beheading evolve such a strong response in you people. Ask yourself a simple question: Would the world be a better place without Matt Ridley? Need I answer that question?’”

Lord Ridley went on to say that the repetition by “Bluecloud” showed he had not been “misunderstood in his death threat”. He also pointed out that the comment was made a few days before the beheading of a Japanese hostage in Syria.

There was a further comment that identified “Bluecloud” as Gary Evans. The comment that “outed” him was removed by moderators but the two comments by him as “Bluecloud”, which involved beheading, were not.

This lies at the heart of Lord Ridley’s complaint. He wrote to me on 30 January: “Incredibly, this comment, outing Mr Evans, was then removed by the moderators, because apparently it was more offensive to the Guardian community than the recommendation that I be beheaded…Accordingly, I would like to lodge a formal complaint that the Guardian censored criticism of a Guardian contributor who twice made explicit death threats against a named individual, while not censoring the death threats themselves, and refused reasonable requests for redress.”

Lord Ridley wanted a public apology.

The Guardian’s moderation team oversee 50,000 comments a day. As I responded to Lord Ridley 11 days after his complaint with an apology for delay: “‘Bluecloud’’s beheading comment was posted on 22 January at 11.32am. The moderators didn’t remove it immediately because it wasn’t seen as a credible threat at that time; the tone and nature of the comment suggested that it wasn’t serious and thus fell into the realms of bad taste rather than a genuine wish that you be harmed.

“However, a moderator took it down the next day (23) at 9.47pm because the story about the Isis hostages was now dominating the news agenda.” The moderators felt this context made the comment cross into something beyond bad taste whatever the original intent. In total it was up for nearly 35 hours. The comment outing “Bluecloud” was removed because it is against the Guardian’s community guidelines to identify any poster. However, a link in his Guardian profile goes back to his own blog, which identifies him although that was not immediately apparent when the comment was taken down.

I contacted Evans, who wrote one piece for the Guardian five years ago and is thoroughly contrite and apologised for his “stupid” comments: “I will not seek to defend them and I apologise for any trouble this may have caused to anyone involved. My first comment was made without thinking as a provocative response to the zombie image. The second was really inexcusable. It was too late for me to apologise on the thread by the time I had found the time to consider my actions.”

The web and particularly the threads are a robust environment but I think we should have taken the beheading comment down as soon as it was reported, even though I agree with the moderators that it was an attempt at a joke rather than anything else. I think the “Bluecloud” comment falls squarely within rule 3 of the Community guidelines: “We understand that people often feel strongly about issues debated on the site, but we will consider removing any content that others might find extremely offensive or threatening.”

When beheadings have been such a tragic part of the news agenda for so many months the choice of a severed head as the accompanying photograph was an error. It seems unlikely to me that the offending comments would have been made had the picture not been what it was. For that reason and the length of time it took to remove the comments, I think Lord Ridley deserves an apology, which I am happy to give on behalf of the Guardian.