I thought this was a joke at first, but it appears to be true: the founder of $cientology, L. Ron Hubbard, thought calculus didn't work.
Now, I know a lot of my readers may not like calculus, and may even hate calculus, but to say it's wrong is, well, lunacy. Of course it works! Trying to come up with ways it works in everyday life is like drinking from a firehouse, but let me just make a list based on astronomy.
Calculus is used in:
1: determining planetary positions
2: sending spacecraft to those planets (and there are a zillion ways it's used in this, from calculating how much fuel you use to knowing how much air the astronauts need in space)
3: determining how stars are born, live and die (something we understand pretty well)
4: calculating the tidal force of the Moon (and other planets and moons on each other)
5: calculating the gravitational field of an object
6: understanding basically anything that changes
7: understanding anything that moves
8: Newton's three laws (and his Law of Gravitation) which are the foundation of classical mechanics
9: all of quantum mechanics too, for that matter
10: ad infinitum.
To say that calculus doesn't work is, well, stupid. It's also arrogant, a feature I see a lot in the field of antiscience. An arrogant person doesn't understand a subject and therefore declares it doesn't work. Creationists do this with biology, flat earthers do this with relativity, and Moon Hoax proponents do this with rocketry. Maybe they feel threatened by intelligence.
I am not a genius. I'm pretty well educated, and maybe even smart, but there's still a lot of stuff out there I don't understand. But I don't say it's wrong because I don't understand it, not if there's evidence it works. I will never understand the intricacies of biological development, or the detailed electronic analysis that goes into semiconductor physics, or even the minutiae of many of the fields of astronomy. That just means there are people out there smarter than me, since it's clear this stuff all works. But that doesn't threaten me. I rejoice in it! I love smart people. They help us all understand the world better, and that's one of the best things there is.
Speaking of which, go read what Jennifer Ouellette wrote about calculus. You'll see why I love this stuff.
Tip o' the mortarboard to Kage at the JREF forum for the heads-up on this.