The best explanation that I have come across is from the pen of Jonathan Edwards. He wrote (it's long and nearly 300 years old, but make the effort to think this through):
A crime is more or less heinous,
according as we are under greater or less obligations to the contrary. This is
self-evident; because it is herein that the criminalness or faultiness of any
thing consists, that it is contrary to what we are obliged or bound to, or what
ought to be in us. So the faultiness of one being hating another, is in
proportion to his obligation to love him. The crime of one being despising and
casting contempt on another, is proportionably more or less heinous, as he was
under greater or less obligations to honour him. The fault of disobeying
another, is greater or less, as any one is under greater or less obligations to
obey him. And therefore if there be any being that we are under infinite
obligations to love, and honour, and obey, the contrary towards him must be
infinitely faulty.
Our obligation to love, honour, and obey any being, is in proportion to his loveliness, honourableness, and authority; for that is the very meaning of the words. When we say any one is very lovely, it is the same as to say, that he is one very much to be loved. Or if we say such a one is more honourable than another, the meaning of the words is, that he is one that we are more obliged to honour. If we say any one has great authority over us, it is the same as to say, that he has great right to our subjection and obedience.
Our obligation to love, honour, and obey any being, is in proportion to his loveliness, honourableness, and authority; for that is the very meaning of the words. When we say any one is very lovely, it is the same as to say, that he is one very much to be loved. Or if we say such a one is more honourable than another, the meaning of the words is, that he is one that we are more obliged to honour. If we say any one has great authority over us, it is the same as to say, that he has great right to our subjection and obedience.
But God is a being infinitely
lovely, because he hath infinite excellency and beauty. To have infinite
excellency and beauty, is the same thing as to have infinite loveliness. He is
a being of infinite greatness, majesty, and glory; and therefore he is
infinitely honourable. He is infinitely exalted above the greatest potentates
of the earth, and highest angels in heaven; and therefore he is infinitely more
honourable than they. His authority over us is infinite; and the ground of his
right to our obedience is infinitely strong; for he is infinitely worthy to be
obeyed himself, and we have an absolute, universal, and infinite dependence
upon him.
So that sin against God, being a
violation of infinite obligations, must be a crime infinitely heinous, and so
deserving of infinite punishment.- Nothing is more agreeable to the common
sense of mankind, than that sins committed against any one, must be
proportionably heinous to the dignity of the being offended and abused; as it
is also agreeable to the word of God, I Samuel 2:25. "If one man sin
against another, the judge shall judge him;" (i.e. shall judge him, and
inflict a finite punishment, such as finite judges can inflict;) "but if a
man sin against the Lord, who shall entreat for him?" This was the
aggravation of sin that made Joseph afraid of it. Genesis 39:9. "How shall
I commit this great wickedness, and sin against God?" This was the
aggravation of David's sin, in comparison of which he esteemed all others as nothing,
because they were infinitely exceeded by it. Psalm 51:4. "Against thee,
thee only have I sinned."-The eternity of the punishment of ungodly men
renders it infinite: and it renders it no more than infinite; and therefore
renders no more than proportionable to the heinousness of what they are guilty
of.
This man's utter God-centeredness is such a blessing. For the highly ambitious, here is whole essay from which this quote is taken: The Justice of God in the Damnation of Sinners.