I agree that anything the lost do is tainted, but that does not change the fact that some acts are obviously less tainted than others... by choice.
As for choosing faith, since that has nothing to do with any deeds (Romans 4:4-5) you cannot apply the same conclusion. Faith and works are not only independent ideas in terms of salvation, they are independent ideas in terms of corruption.
Those choices are basicly made for personal edifications
Not always. This is certainly true of many choices, but we can describe choices that cannot be attributed solely to "personal edifications".
Romans 2
14 For when the Gentiles, which have not the law,
do by nature the things contained in the law, these, having not the law, are a law unto themselves:
15 Which shew the work of the law written in their hearts,
their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another...
Men have been given a conscience. They can sear that conscience by repeatedly refusing to heed it (the concsience of the Gentile is his "law" which is designed to lead him to Christ - Gal 4). If a Gentile acts in regard to the law "by nature" and is pricked in his conscience which is his "by nature", that conscience will lead to him to Christ.
Man is designed to have a law (written or conscience) that serves as his schoolmaster to drive him to Christ. He can either heed or ignore (Proverbs 1). If faith is purely an act of God, of what use is a schoolmaster to "lead" anybody?
Faith is not a work. It is the result of acting on the leading of a conscience that will "accuse" us just as the Mosaic Law accuses. No law can save. Law only accuses. But it can lead someone to Christ if its purpose is recognized.
