Is there a difference between sins that offend God, and those that offend the rest of us?
Every culture under the sun recognizes the reality of sin but distinguishes between sins it regards as relatively harmless and sins that are serious. Serious sins are those perceived to be harmful, e.g., murder, adultery, and theft. Even in societies where these things are common, there are penalties.
Knowledge of the true nature of sin is acquired through revelation, not tribal lore or traditions. The biblical revelation is that sin is not primarily an action that offends one's neighbors. True, acts harmful to others are sin, but in its deepest sense sin is an offense against God. And the category sin includes every kind of sin, including the sins we cannot see: sins of the mind.
For instance, Jesus said that to lust after a woman was tantamount to adultery (Matt. 5:27-29). Lust, which is invisible, seldom harms an unsuspecting woman. It is primarily sin against God. David knew that. He had sinned against Bathsheba and her husband Uriah (whom he murdered), and he had sinned against the entire nation he represented as king. Yet in his confession to God, he said, "Against you, you only, have I sinned and done what is evil in your sight" (Ps. 51:4).
That becomes clear to us when we ponder the truth that sin is sin because God says it is. Ultimately, every sin is sin because He defines it as such. Tribal tradition cuts no ice with God. No matter how trivial in our view, deviation from thought or action appropriate to creatures made in His image is sin. If you disagree with this view of sin, try to justify your position with the Bible.