This is insanely hyperbolic.
A Cessna Citation I carries 564 gallons of fuel, with which it can travel ~1,500 miles - 2.7mpg.
A Ford F-250 carries 48 gallons of fuel, with which it can travel ~700 miles - 14mpg.
It's not even 10x.
Similarly, my chain saw probably pollutes nearly as much as my new Honda truck even though it only gets a few gallons of gas per year.
What if the little person and the wealthy person travel a different # of miles?
No amount of cherry picking is gonna get you to the 10,000x number upthread.
Just searching the article for "lead" only gets this quote: "The possibility of environmental legislation banning the use of leaded avgas (fuel in spark-ignited internal combustion engine, which usually contains tetraethyllead (TEL), a toxic substance added to prevent engine knocking), and the lack of a replacement fuel with similar performance, has left aircraft designers and pilot's organizations searching for alternative engines for use in small aircraft."
Also a reference to "Planemakers challenged to find unleaded fuel option - The Wichita Eagle" a 2009 article which has a dead link.
Curious to me why you would cite an article that says the opposite of your assertion and then repeat the definitive statement. I must be missing something.
The planes you are thinking of are mostly used for hobby flying or some short haul commercial flights, e.g. float planes. These have piston engines, more like your car ICE.
I cherry-pick "5 miles in a F-150" vs "5000 miles in a Citation."
Cherry-pick complete.
> In the fifty years following the 1969 first flight, more than 7,500 [Cessna] Citations were delivered, forming the largest business jet fleet.
The math is similar for a Gulfstream, if you prefer.
I'd also add that two wrongs don't make a right, and while not strict enough there are emissions regulations for aviation.