Some people should move through the pain. There's no magic words which transform people's mind. Bitcoin is for everyone not for everybody.
The best way - teach people day by day, step by step.
I usually tell people story about my bank than blocked my transaction and didn't want to give my money back in 2008 crisis. Tell them how cool to be the only owner of your money. Tell them why should I store private key, etc. And you know what, they store their sats on Binance.
Maybe a good idea would be to store their sats on my wallet and when they'll be ready give them it back.
p.s. or don't give them it back, so they'll understand why self custody is so cool
Per aspera ad astra