"If you drew a continuum and on one end was kindness and compassion - and that's Buddhism - I would have put Islam at the other end, the raving loonies, the guys who blow things up."
But little things began to change his mind.
When he was teaching in Singapore during the Ramadan fasting month, he noticed a group of Muslim children laughing after school.
"What I was seeing was a strength I didn't have or didn't know I had, which is the ability to do without yet just be normal."
But he found his "Western pride" was a stumbling block.
He spoke to the owner of a Muslim bookstore. "I said, 'I don't know why I need this. I try to go through life in a decent fashion, and don't mess up anyone else's life. Why do I need a system like this?'
"He took a blank piece of paper and said, 'Write down a list of the reasons you can't be Muslim'. I couldn't think of any so he sort of signed me up to the club, so to speak."
Green tries not to express too much convert's zeal.
"What I do is what I do and what you do is what you do. Ideally, I wouldn't tell anyone. I don't think we should trade labels.
"I'd prefer a situation where you don't tell anyone what your beliefs are but they think, 'He is a really good human being, a really decent bloke.' Unfortunately I find myself having to explain."
Green moved to New Zealand 16 years ago and lives in Christchurch. He'd like a quiet life but speaks out against the violence being perpetrated in the name of Islam.
"To be slitting throats of people, to be abducting people just because they are not Muslim according to your definition - these kinds of things are so far off the bloody scale that they beggar belief to me and to many others.
"There's a distressing imbalance in seeing something far more profound in the teaching that isn't coming across at all."
