So.... if I shoot someone died because I think they are better off dead or because I think it will glorify God, then it's not sinful in your morality?
An abortionist who kills the baby because the mother says she's not able to deal with it, to you then that's a wonderful, righteous, God-pleasing thing?
I find your morality ( a radical but strange twist on "situation ethics") to be disgusting.
IMO, sin is anything that is short of God's perfect, holy, loving will... especially as revealed in His Law. Sin literally means "to miss the mark" We are to be as holy as God, as loving as God, as moral as God....and to perfectly, completely ulfill His law, 24/7, in thought, word and deed.... all that is "short" of that is by definition sin.
Now, back to the topic.