"I took a water bottle and filled it up, and when we got back to base I boiled it up (in case of E. coli, etc) and made a cup of tea. I drank it in front of a few antis to show I wasn't worried about residual 1080 in waterways."
No one had offered to join him, he added. A few had looked "genuinely worried" and while most left before he did, some saw him drink it.
"My strong suspicion is that a lot of well meaning people who genuinely care for the environment have had their emotions hijacked by emotive propaganda — movies of dying dogs or dead deer," Mr Finlayson said.
Some were trying to pass off misinformation as science, and that, combined with a strong anti-government feeling in some quarters, was creating a lightning rod for "so-called activism".
More encouragingly, he had raised the "obvious need" for training young people in kaitiakitanga, and had found solid common ground.
Last month Mr Finlayson wrote in his Northland Age column that he doubted he had ever encountered a topic that elicited such emotional attachment and dogged unwillingness to engage in the facts as 1080.
"When we meet in person there is feedback from body language and other controls that (usually) moderate the conversation. As more of us go online and use social media, many people seem to park those constraints and feel that they can just let rip," he wrote.
Posting what he believed to be a well-balanced Newshub documentary, which summed up the pros and cons of 1080 on his Facebook page had attracted all manner of allegations, along with threats of violence.
"Delving deeper, I realised that a lot of people who are genuinely concerned about our environment and animals have had their emotions hijacked by the type of emotive propaganda that would make Goebbels proud," he added.
"Once this happens logic and reason seem to take a back seat. Science is labelled as 'government propaganda'. The more evidence of the success of 1080 programmes that is provided the harder the opposite opinion is held. Confirmation bias, where any snippet of information, no matter how untenable, is instantly believed and proliferates."
Facebook had also connected him with some more moderate people who genuinely wanted to protect the natural environment but had serious concerns about aerial drops of 1080, however, and meeting those people had been much more rewarding than "duelling it out with keyboard warriors".