"You can feel very good about the organic potatoes you buy from a farm near your home, but half the emissions—and half the footprint—from those potatoes could come from the energy you use to cook them. If you leave the lid off, boil them at a high heat, and then mash your potatoes, from a carbon standpoint you might as well drive to McDonald’s and spend your money buying an order of French fries.”(*) No, I've never heard of any of these people either.
Good intentions and intuition aren't enough. Eventually somebody has to do some arithmetic.
The good thing about a carbon tax is it saves everyone the trouble. No need to think about whether food miles are important. Whether they are or not, the carbon tax will do the arithmetic for you and let you know.