Dr Holt strongly believes much of homeopathy's success is based on the placebo effect and false information.
"Either homeopathy works, or, what we know about chemistry, physics, medicine, pharmacology and many other sciences is wrong," he said.
"Homeopathy is the scientific equivalent of insisting that the sun rotates around the earth. That may have been acceptable hundreds of years ago before we knew how things worked, but now, you'd have to be insane to believe that."
New Zealand Skeptics agree.
The organisation's media spokesperson Vicki Hyde said homeopathic remedies verged on the "ridiculous", including grinding down and diluting oysters.
"They say oysters are good against constipation because they're tightly closed and you're tightly closed. They dilute it right down but say it works because once upon a time the oyster remembers it was closed. It's like tonic with one drop of gin, which is not much of a drink."
Last year, five researchers, from New Zealand and the UK, called on doctors to stop prescribing homeopathic remedies or referring their patients to homeopathic practitioners, on the grounds that such behaviour is "not consistent with the ethical or regulatory requirements of practising medicine".
It's the kind of thing that gets homeopath's hot under the collar.
Tauranga homeopath Clive Stuart said a homeopathic remedy generated an electro-magnetic charge when the mixture was shaken and diluted. The charge is amplified at each step of the dilution process.
"So lack of molecules does not mean lack of effect," he said.
He argued the placebo effect couldn't be true when homeopathy worked on children and animals.
"There is enough positive research to merit further investigation of it's potential to relieve suffering," Stuart said. "It deserves much more than the denialism of a closed mind."
Tauranga GP and homeopath Dr Kerry Clancey said enough research had been done to show there were effects from homeopathy different from placebos.
She said homeopathy worked at a level technology could not yet explain.
"When you've been a GP for 25 plus years you get a sense of when something works and when something doesn't."