Personally, I think if there were a god, that god would be "big enough" not to be offended by things we do or don't do. And if that god were not "big enough", then I would not call it a god.
Christians understand God to be entirely good without the slightest impurity. His virtue and justice is total in such a way that we human beings cannot comprehend. As such, nothing which falls short of this total virtue can stand before God as any impurity, any lingering evil is incompatible with the direct experience of God's love. Sin is simply that which falls short of the moral virtue God demands of us, and as such it is punished in so far as to fall into sin is to lose salvific grace. Without cooperating with God, we cannot achieve the virtue otherwise required for salvation because no fallen human being is going to be perfect by their own power. If we cooperate, God takes our imperfections on to himself through the cross. (But you can reject that)
It is not so much that God is hurt by our sin, but that by being sinful one's will is turned away from God which if obstinate will result in the loss of the soul. God is merciful, but because he is so incomprehensibly good he is also unrelentingly just. Not the slightest unrepentant evil will go unaddressed, not because God is petty, but because he is so uncompromisingly good. If you die unrepentant of wilful sin, you cannot expect God to degrade his own justice and overlook it. Instead God will give you the very thing you want, an eternity without the experience of God where no hope, love or joy can possibly exist.
God is light brighter than all the stars. And those whose wills are determined to darkness will not be able to stand within that light. That is why sin is so damaging. Not because God's light is threatened, but because it makes
us incompatible with God's light.
