They're saying that at highway speeds the cars energy usage would be off the chart, or if they scaled the chart to that usage, everything else would be too small to discern the differences.

You guys are in agreement.

The measure of productivity of transportation is distance traveled, not speed (unless this were some time race). Comparing kw/speed tells you nothing about the kWh used to make the same trip as alternative modes of transportation.

In theory I agree, in practice other stuff, as the need for heating/cooling, really muddled the theory and puts the sweet spot speed way up. And if we turn the Aircon off, 150 is a really high number.

Wdym? The faster a car moves (or anything, not just a car) the less efficient it's gonna be, because it has to fight against more and more wind resistance.

That isn't entirely true. At lower speeds there may be other inefficiencies that are worse than wind resistance (since wind resistance becomes negligible at low speeds).

It will depend on the vehicle, but for example, small gasoline cars are more efficient at ~70 km/h than at lower speeds. Electric vehicles will likely be more efficient at lower speeds (~40 km/h) than gas vehicles, due to (lack of) gearing but there will still be low speeds where they are less efficient than higher speeds.

https://www.researchgate.net/figure/ehicle-energy-economy-at-different-speeds_fig1_326822085