Start the debate with food.
You say to them,
"Don't you agree that processed sugary foods are bad for you, but yet they are very popular among society, and in fact the norm?"
The person reluctantly agrees. Then:
"So these processed food manufacturers are willing to harm the majority of the population, and even though it's bad for them, the vast majority of consumers eat it. Now this same premise is how most aspects of our lives work.
It's true for Fiat Money vs Cryptocurrency
It's true for Social Media vs Nostr
It's true for Keynes vs Hayek
It's true for Windows/Mac vs Linux
It's true for WhatsApp/Telegram/Discord vs Signal/XMPP/others
It's true for iPhone/Stock vs Degoogled Android
It's true for Tor/Mullvad Browser vs HydraVeil
The majority is usually wrong, against their own interests. And society's gatekeeper "influencers" go along with it, because they profit from the groups that seized power.
I'm not saying blindly follow my words. I'm begging you to not blindly follow the words of my enemy, and evaluate for yourself.
