I think their point is that a straightforward reading of the statement “this had good consequences for all of humanity” would need to be evaluated by examining

I think their point is that a straightforward reading of the statement “this had good consequences for all of humanity” would need to be evaluated by examining the finite equivalent “there does not exist a member of humanity for whom this had bad consequences”. Hence they propose an asterisk next to “all”, because “all of humanity” means something more like “humanity as a whole (decided by someone?)” or “humanity (the ones who aren’t dead?)”