From A Leveringhaus, on the ICRC blog, considering psychological as opposed to geographic distance:
…geographical distance does not automatically result in psychological distance. After all, radical Hutus who set out, during the Rwandan genocide in 1994, to ‘crush cockroaches’ by hacking their Tutsi or moderate Hutu neighbours to do death were psychologically distant from, yet geographically close to, their victims. Conversely, drone operators who report post-traumatic stress are geographically distant from, yet psychologically close to, events on the battlefield. The relationship between geographical and psychological distance is anything but straightforward.
In short, one might expect that that which causes greater psychological distance at a societywide level (whether imbued by fake news or intentionally manipulative forum content, caused by dehumanizing Zersetzung-style campaigns, or other) will increase the general capacity for really bad stuff – unless in a particular sociopolitical, geopolitical and technological context there are some reasons to think otherwise.
The article also discusses other concepts of “distance” (causal distance related to chain of command; temporal distance with the example of a landmine) as pertains to moral and legal dimensions of engaging in hostilities in conflict.
In terms of International Humanitarian Law, where the yardstick is the legal criteria of distinction, proportionality and precautions, the following challenge can be cited with respect to causal distance:
…if the causal chain that led to a war crime is particularly long and complex, it may diminish individual (criminal) responsibility for that crime. For one thing, it may become difficult to determine who has done what. And even if it was possible to do so, none of the many agents who acted within the causal chain may have contributed enough to be held responsible for the resulting war crime. Everyone, in other words, does a little bit to contribute to the crime but not enough to be held responsible for it.