I agree with you on the fact that Christians do take for granted His Salvation, and go on sinning... they do this, as I understand, because they have no root in themselves.. I did it because I didn't know who I was, and I didn't truly believe (tho I thought I did) or understand (tho I thought I did) everything I read and saw. Everyone that does this is wrong, and they God will tell them so, just like He told me.
Paul said in his epistle to the Phillipians, c2v12, "work out your own salvation with fear and trembling." I believe that speaks of the fear in Job 28:28 where it says "And to man He said, 'Behold, the fear of the Lord, that is wisdom, and to depart from evil is understanding.'" If I were to just worry about morality, I would be like you, defining morality by whatever legal means I could, and I would be perfectly happy... as it is, I fear the wrath of the Almighty. If you want to classify me as primative for this, cool with me... but if you're going to try to prove my justifications wrong, at least understand the material I've contrived them from.