Not being around for the consequences of being in a sexual relationship is sexual irresponsiblity. The very fact that Jason was born not knowing who his father is shows that Superman was irresponsible. If he wasn't sexually irresponsible then he has nothing to be sorry for in the film. THe only reason leaving w/o a goodbye was wrong was because he and Lois were in a sexual relationship and presumably in a comitted romantic relationship as well. If you deny sexual irresponsiblity then you deny any wrongdoing on Superman's part. And the whole point of this aspect of the film is that he made a mistake. It just so happens that the mistake is one of sexual irresponsibility.