This sounds like the "We Should Improve Society Somewhat" meme.

"I want to be more eco-friendly." "And yet you do things that are not eco-friendly. I am very intelligent."

Your 0km friend must be particularly ignorant as to not realize that his coffee, his wine, his beer, his meat, his flour, his electricity, his phone, his clothes, and so on, are not made in the same place where he lives. This is highly a-typical - nothing to base an argument on.

The localvores I've heard about use the phrase "Marco Polo exception" to allow 'anything your average 13th century explorer might have brought back from distant lands. So: pepper, and turmeric, and even the odd knob of ginger root stayed in the larder.'

> living on private cars in vast Rivieras do pollute GLOBALLY much LESS

Citation needed.

Single-family homes are more expensive per person than shared buildings. You have higher heating bills because you have no common walls with others.

You have worse economy of scale in your water, sewage, power supply, and internet and phone service provider. Or, if you have your own well, or septic system, you have to spend more time to maintain it.

You must dedicate more room to storage or spend more time resource planning - if a light bulb burns out, I can walk to the store to buy a replacement while you either go without for a while, or you store more extras than I do, or you keep better track of your bulbs than I do. (The same applies for every consumable: batteries, toothpaste, tape, etc.)

You have to drive to visit the doctor, dentist, barber, and so on, while I can walk or take shared mass transit with frequent service. Assuming you have older kids, they need to travel school and visit friends.

Even the road to your house is more expensive to maintain than one in a city, which adds to your carbon footprint.

But even that is hand-waving on my part. So, to the literature! Here are snippets from three papers I found:

] Studies using the consumer's carbon footprint method usually reveal only small differences, either in favour off or against emission savings in cities. What are the reasons for the balance to shift in one or the other direction? This article, based on Germany, points to higher emissions in rural areas, while our own follow-up study on Bavaria shows the opposite: higher emissions in cities (Gill and Schubert, under review). - https://www.sciencedirect.com/science/article/pii/S092180091...

] Predominantly urban households contribute to about 650 kgCO2 e/cap less on average compared to their rural counterparts on the regional level of data aggregation. https://iopscience.iop.org/article/10.1088/1748-9326/aa6da9/...

] In Eastern Europe, carbon footprints ... increase clearly with the increasing degree of urbanisation. By contrast, in some Western European countries, such as France and
Belgium, carbon footprints clearly decrease with the increasing degree of urbanisation, even when income is controlled. Overall in the studied countries, carbon footprints are 7% lower in cities than in rural areas when income and household characteristics are controlled. However, this is compensated by the 6% higher average income in cities. - https://iopscience.iop.org/article/10.1088/1748-9326/ab443d/...

Looks like the research evidence is that rural populations like where you live do NOT "pollute GLOBALLY much LESS" than urban populations like where you used to live.