These are not serious people

If you believe it to be a good idea to remove GST from food, whether all food or just some food, at least one of three things is true.

1. You have not thought this through or read anything from anyone who has thought this through. Labour's 2018 Tax Working Group showed that, for the same cost to government revenues as a food-sized hole in GST, you could provide a transfer to every household. That transfer would provide twice as much benefit to poor households as taking GST off of food. Please read Paragraph 33 of the TWG report and reconsider your position.  
2. You have tried to think this through but are, in fact, an idiot. You are neither able to do basic math nor to listen to anyone who is able to do math. Not being able to listen to people who obviously know more than you do about a specialist topic suggests you really are unfit for politics. You will do harm to the people you purport to represent and wish to help, through willful stupidity. This will be a general problem across all policy areas, if you have revealed that this is your type. 
3. You are pandering to people who you think are unlikely to think this through, or who you think are unable to think this through. In this case, you are, in fact, evil. You are proposing something to people who you think are too dumb to know any better, that will make them far worse off relative to other policies that cost just as much. 

I can believe that Te Pati Maori have not thought this through and have not bothered to read anything from anyone who has thought this through.

Too much of the rest of their tax policy sounds like Trump promising to build the wall and make Mexico pay for it. 

If Labour goes for this, it's firmly Category 3. They know better. They have time to reconsider. I really really hope they reconsider. 

Susan Edmunds at Stuff asked me for comment on it yesterday; Thomas Coughlin at Herald caught my bit on TVNZ Breakfast this morning.

I'd gone through the absurdities of exemptions a while back; it all still holds.