You're both right.

Hard money only would impose a structural obstacle that can still be overcome to achieve nefarious goals like war. But it's not a silver bullet for solving problems caused by our innate tendencies:

Humanities biggest strengths (tribalism, empathy, cooperation) are also its biggest weaknesses (groupthink, weaponization of emotions, systemic overshoot). Technology *could* change that because it codes behavior. But that would require software (culture) to override hardware (above mentioned tendencies hardcoded into our genes). 

The only way you could achieve this is by literal brainwashing of civilizations with new objectives overriding our evolutionary ones. The Culture by Bainks is a good fictional example of this. North Korea comes closest to a real-world example, albeit a distorted one.

Hard money alone is just a one tool in a hypothetical set of tools that would be needed to fix this.