Your friend believes in Earth? PFFFFT, poseur, everyone knows we live in a simultion! How else do you explain the dead pixels in the "sky" and the dude who respawned in 3 days?
Anyway, kidding aside, I'm sorry to hear you know someone who went full flat-earther. It's crazy that we have so much information, videos showing the curvature of the planet, etc, and people still actually believe in a flat earth to such a degree.
On my end, it's comforting that the conspiracy theorist nutjob I used to know didn't go that far.
This was a man who was full 9/11 truther ("It was a coverup to hide wall street fraud, and get us into endless war!"), who is full on Illuminati-control-everything, that the illuminati use hollywood to make us subliminally believe in the end of the world so we submit to them, and thinks the pope controls ALL the world governments, that the catholic church literally worships lucifer, that vaccines are secretly a eugenics program designed by bill gates to kill black people, and unquestioningly shared articles from a site that said AIDS medicine CAUSES AIDS, etc.
And even he was like "Yeah flat earthers are freakin' stupid, we have way too much video proof that it's round."
Then again, he's also terribad with allegory and metaphor. He legit didn't get the central twist of the Lego Movie and was like "waaaaaaaat reaaaaally?" when I explained it to him. XD