My father-in-law doesn't believe that the moon landings took place. All the data in the world cannot convince him otherwise. The only good strategy in the face of these types of claims is to go up the crazy scale. For example when he tells me that the moon landings didn't happen, I tell him he's naive it he thinks the moon exists. The moon was blown up in the 50's due to a nuclear test gone wrong and what we're seeing now is an artificial projection.
I firmly believe that gravity is caused by a bunch of invisible garden gnomes that hold you down. Does anyone have the data to refute these claims?
https://www.scientificamerican.com/article/chlorofluorocarbo...
Also, see the definition of homosphere:
https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Other_laye...
"The homosphere and heterosphere are defined by whether the atmospheric gases are well mixed. The surface-based homosphere includes the troposphere, stratosphere, mesosphere, and the lowest part of the thermosphere, where the chemical composition of the atmosphere does not depend on molecular weight because the gases are mixed by turbulence. This relatively homogeneous layer ends at the turbopause found at about 100 km (62 mi; 330,000 ft), the very edge of space itself as accepted by the FAI, which places it about 20 km (12 mi; 66,000 ft) above the mesopause."
Note that the ozone layer is well within the homosphere so CFCs readily mix into it from surface emissions.
Going up the crazy scale: Has he burst into flames? If no, then air mixes heavier and lighter components. If yes, then the 21% O2 is actually at the bottom and should be 100% as it is heavier than N2.
Also if you lie down on the ground do you suffocate to death because of all of that heavy ozone hanging around there? No, because it's dispersed throughout the atmosphere.
Ultimately it sounds like the kind of situation where no amount of logic is going to change his mind and that you're probably better off avoiding the subject entirely for the sake of your own sanity.
This is not to say that established theories would always hold scrutiny. Thinking of e.g. what we thought about tectonic plate movements/continental drift only ~100 years a go.
The makeup down here is largely controller by convection and turbulences, only farther up the relative weight starts to matter.