When you sin, what have you been calling it?
This of course is the problem with people who think what is written in their own minds, is more important than what is written on paper.
Sin is what God says it is. God tells man what sin is. Man does not tell God what sin is, because all sin is against God, and God is the One that judges all sins of men. It's not the other way around.
Therefore, the statement that sin is
only transgression of the law of God is false.
All unrighteousness is sin.
Anything unrighteous, whether in thought, word, or deed is sinning against God, which is why lusting from the heart is already sinning against God. Before any work of the flesh is committed, which is sinning against God in the flesh, the sinner has already sinned against God spiritually in the heart and the mind:
And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled.
By one simple Scripture your whole argument to try and make works of the flesh doing wrong for you, but not sinning to God, falls apart. All works of the flesh are called unrighteousness of the unrighteous, that shall not inherit the kingdom of God, and all unrighteousness is sin. All the unrighteous doers of the works of the flesh are called by God: Sinners, whether believers or not.
Scripture makes no difference between unrighteously sinning believers, or unrighteously sinning nonbelievers. We are what we do in sight of God, not what we say or believe we are.
Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.
This one Scripture disanulls every false teaching that says anyone can be righteous by faith alone in sight of God, while also doing unrighteousness in His face.
The thing is, knowing these things perfectly is easy, by just reading them and taking God at His word. It's the doing of them that matters most.
But be ye doers of the word, and not hearers only, deceiving your own selves.
Sinful men want to make things complicated and confusing, and so try to change and twist Scripture around into their own imagination of what is sinning or not.