Benefit or harm
Discussion of inherent harm or benefit is the only reliable basis upon which a rational or reasonable decision may be reached, at least with regard to large issues.
It has been argued that this idea is essentially equivalent to moral relativism, or the ends justify the means, in that if the results are "good" enough, they counterbalance any "bad" committed. This is only true, however, if the badness (immorality) of the original act is not included in the sum total. (If the moral values upon which that original act is judged are in turn based on reasonable arguments, those arguments may become part of the discussion; if they are based on dogma, doctrine, or other "revealed truth" (i.e. argument from authority), then the discussion can go no further since the premises are hidden inside a black box.)