if they're like a wise guy they'll be like oh Christianity will allow you to do anything and then just repent for it and tadaaah Jesus will forgive you!
First of all, God deals with wise guys who think that they can get away with crap and repent after like it's a game.
Secondly, what does the Old Testament say?
"Let the wicked forsake his way and the evil man his thoughts. Let him turn to the Lord, and he will have mercy on him, and to our God, for he will freely pardon." Isaiah 55:7
Wow so, with this, and my recent post on original sin, it seems that except for the Jesus part, Christianity and Judaism is in fact closer than some people may have previously thought.