You're not in a position to make that judgement, and you're arrogant if you think you are. God is the only one who can make such an assessment of my soul. I am a Christian because I've followed the Biblical path to salvation and I live my life and conduct my family life in a Christian manner.
I also am aware that we live in a free society. The freedom that someone has to read 'Harry Potter' is the same freedom I have to worship God as He sees fit. It's called the First Amendment. I think we should keep it.