Driving to your local grocery and flying private are orders (plural) of magnitude different in terms of carbon footprint. If your local grocery is 10km away, you'll save ~2.5kg of C02 if you cycle instead of drive[1]. If you fly for three hours, you'll save ~700kg of C02 if you choose to fly commercial instead of private[2]. I don't see how the _former_ is "way more extreme".
Yes, nobody is disagreeing with that, and in rare cases only private will be possible, but other greener options are almost always available. The greenest one usually being: not flying at all.