I’m not sure who the target of the persuasion would be here; those about to commit it, or the global community to intervene.
If someone has arrived at the conclusion to commit genocide you have very few options to prevent it. Many historical genocides have targeted people for historical, religious, political, and scapegoating reasons. There is often such a fear involved for the people group in power that is real, palatable, and often overwhelming. When the genocide starts it is very much an us or them event. The internet might be a useful tool here to inform the general population that their situation is not as bad as they are told, and to provide avenues for reporting atrocities.
For the global community there is already a lot being done. The UN, regional coalitions, and many NGOs work on documenting, proving, and stoping genocide. The challenge is that these are major geopolitical movements that happen within a sovereign state. Often it is that states ruling institution that is behind it. Its frustrating but I don’t know of a better way to address genocide externally aside from. There may be tools to be built/managed externally for those to use in the affected region to report/document. Though many governments can manage/control the internet and access to information. For as distributed as the internet is there are still a very small number of backbone pieces you’d need to adjust to block/restrict content.