This will be something of a unhelpful and unpopular answer, by you probably can’t.
What would convince you to stop eating meat from factory farms? What would convince you to only buy electronics from completely ethically sourced companies? What would convince you to only eat healthy nutritional food? To exercise regularly? So on and so forth?
There are many good and important, but inconvenient, things to do. But for most folks, the first step is wanting to. If he doesn’t, it will be an uphill battle.
Your not wrong, though that kinda re-enforces my point. What would it take to convince a society to abandon an inherently unethical economic system?