This is sometimes pitted against all sorts of verses (including 1 John 1:8-10) that say we are all sinners. But look at 3:5-8:

> But you know that he appeared so that he might take away our sins. And in him is no sin. No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him. Dear children, do not let anyone lead you astray. He who does what is right is righteous, just as he is righteous. He who does what is sinful is of the devil, because the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the devil's work

Verse 9 thus refers to a time after God takes away our sins. Whether 3:9 means that, in God's eyes, we no longer sin because our sins are cleansed by Jesus Christ; or, whether it means that someone born of God does not go on habitually sinning; or, whether it is no more an absolute than the ancient proverb "a wise man cannot fall" is a matter of discussion; but clearly, this single verse can't be used in opposition to any other which calls us all sinners.