Their good works will not save them. Remind them of that. Once we come to the cross, embrace it, and commune with our Lord, we are to turn from sin, not practice it. The mark of a real Christian is one that loves, and one that is striving against sin, not embracing it. We do not have to ask Christ in again for every sin, but we are to confess it and attempt to sin no more. We have struggles with some sins, and that does not affect our true faith, but if we openly practice sin, which means that we deliberately do (in-your-face) some kind of sin, Scripture warns us that there is no longer any sacrifice for that and you are in dire straights. There is need for concern for one who thinks that sin has no consequences.