So how is it that you can deny the plain teaching of Romans 3:12 when it is clearly set before you?
Do you have some other scripture that tells you that Romans 3:12 is somehow null and void?
Does the scripture contradict itself?
Yes, this is the Scripture that seems to throw everybody off. Paul frequently uses examples--sometimes hyperboles--to demonstrate a point. In this case, he shows how Israel is completely engulfed in sin as a nation--a nation that had formerly been called to be a completely righteous nation.
So one has to ask himself: how can a righteous nation eventually become completely profligate and corrupt, to the nth degree? Paul's argument is that we all have a nature that is susceptible to the influence of sin. If Adam and Eve were susceptible to the temptation of the serpent, then all Israel was susceptible to corruption and apostasy.
Paul was not arguing that all men have to descend into the abyss of complete depravity. He was only showing that if at a time in Israel's history such a thing happened, then certainly all men are susceptible to sin. If a righteous nation can fall, then all men, pagan or not, can fall!
In other words, Paul was saying that all men in Israel *at that time* had developed horrible mouths and wicked actions. He was not saying that all men have to do this, but that since all men at one time did, then all men at all times can!
We are all stained with sin, and are excluded from the Kingdom of God unless we are cleansed by God. Even if we are righteous, we still need the atonement of Christ to be given entry into the Kingdom of God.
And this is because sin is in us, and renders us not only capable of great sin, but also guilty of the smallest sins. All sin excludes us from the Kingdom of God. It does not require the greatest sins to be excluded from heaven--only a denial of Christ's atonement, which alone sets us on a course that leads to eternal life and immortality.
Only our embrace of Christ's atonement covers all our sins, because only Christ represents a complete denial of *all* sin! Only he was sinless. Only his righteousness qualifies us for eternal life.