I think you might have missed my point. I'm not saying that dark matter skeptics are crackpots because they don't believe in dark matter. I'm saying that if people think they can disprove the existence of dark matter because you can apply some high school arithmetic and claim that Keplerian law is violated, then you
are a crackpot.
Someone else unwittingly suggested a parallel to Fermat, which I think hits the nail on the head exactly. If someone thinks they can prove Fermat's last theorem with some high school geometry, odds are pretty good they're a crackpot. If they're a well-regarded mathematician and they can build off new mathematics and make a few very complicated leaps by discovering new mathematics of their own, then people take them more seriously.
Scott Aaronson has a really great take on this here: https://www.scottaaronson.com/blog/?p=304
As an aside that's probably only interesting to me, I went to a Great Books college. It's one of those hippy dippy liberal arts schools where there are no electives, no textbooks, no lectures, just primary sources. You learn mathematics by reading Euclid, Ptolemy, Newton, etc.
At any rate, for first-year "Labratory" class, you trace the atomic theory from the Greeks to roughly Avogadro. Along the way you read papers by and replicate the experiments of many influencial scientists along the way. When I mention that the above crackpots are "wrong", I don't mean it in the sense of the aether or analogous theories along the way to the atomic theory, namely phlogiston or caloric, two previous theories of heat. Those theories did not explain new observations and were rightly discarded along the way. Priestly and Lavoisier were brilliant and tried to make theory match observation, so now even though their theories are discarded, their work still stands on its own for the time. I wouldn't call them wrong. There's a definite difference between them and theories that are just wrong.
Nobody's going to get a Nobel Prize when they just make the world believe that they have obviated the need for dark matter by pulling out some high school math and some Kepler proofs.
Someone will win it if they ever make an observation that proves a MOND theory in a way that shows conclusively that dark matter is not needed to explain all current observations and in fact cannot remain compatible with this new observation.
There's a big difference between the two, I think.