the tails would partially cancel out in expected impact estimates because many actions with potentially high positive impact could also have potentially high negative impact if any of our assumptions are wrong?
Yes. For example, cost-effectiveness analyses of global health and development interventions assume that saving lives is good, but this may not be so due to effects on animals. A lower cost to save a life will be associated not only with generating more nearterm human welfare per $ (right tail; good), but also with generating more nearterm animal suffering per $ (left tail; bad), since the people who were saved would likely consume factory-farmed animals (see meat eater problem).
Yes. For example, cost-effectiveness analyses of global health and development interventions assume that saving lives is good, but this may not be so due to effects on animals. A lower cost to save a life will be associated not only with generating more nearterm human welfare per $ (right tail; good), but also with generating more nearterm animal suffering per $ (left tail; bad), since the people who were saved would likely consume factory-farmed animals (see meat eater problem).