EarthsShadow said:
...I basically told him that in some ways alignments are a waste of paper space and time and effort because each single person will have his or her own interpretation and can justify almost any action within almost all the alignments ...
True, but a bit beside the point.
I think people tend to go wrong a bit here - in thinking about alignments and justifying single actions. Alignment isn't really about individual actions, it's about patterns of behavior. Alignment is the result of the characters
long term behavior and motivations.
The PHB mentions this - the basic difference between someone who is "neutral" and one who sits an extreme (law, evil, good, or chaos) is
commitment (be it conscious or unconscious) to an ideal. If overall, the record shows that the character hurts others when they could choose not to, he or she is Evil. If they regularly stick their necks out to make life better for others, they're Good. Similarly for Law and Chaos. It's far less a matter of individual instances, and more a matter of what happens in general.
Players and DMs would have fewer disagreements on the matter if they approach it this way. If the DM can say - "Look at how many people Joe Hero has harmed for his own profit," Joe Hero's player will have a much harder time justifying it as non-evil. And if the DM can't come up with a list of misdeeds long enough to make justification seems silly, then he probably doesn't have a strong enough case for a general change in behavior and alignment.