"What is the most impactful way to ensure that everyone has sufficient clean water and nutritious food to survive? Would approach X or approach Y or approach Z save more lives? What other alternatives should we be considering? What are the tradeoffs and risks here? How can we hedge our bets to protect against those tradeoffs and risks?"
Reasonable people can and should have interesting conversations about how best to solve problems. Those arguments could even get heated, but at the end of the day, the person you're arguing with is aligned on key values with you, and just disagrees on how best to fulfill those values.