If we should say that we are in a state of not having sin, we make Him a liar, and His word is not in us, 1 John 1:10.
We are washed from our sins; however, we may still sin. This does not change the fact that we have been washed, for the one who has bathed only needs to cleanse his feet (John 13:10). Sin can still affect the grace believer who is not walking in the truth—whether by failing to have victory over the sin nature, by being fond of the world system, or by being persuaded by Satan to act independently from God.
Ignoring our sin is not righteous. We are to confess (verbally agree with God) that our actions are sin, and take the way of escape in order to overcome the enemy who seeks to persuade us to act in a lawless manner.