To add to the first thought below: There is also a difference between ‘conceptually justified’ and ‘practically justified.’ That is, something may be morally justifiable in an abstract, conceptual form, but its implementation is beset by so many moral caveats as to be practically illicit. Thus, one could make the argument that, say, slavery in and of itself  (the legal state of owning another human being) is not morally wrong, but that practically speaking it can’t be implemented without moral abuses and so should be considered immoral.