I hate seeing so many people judging others without instruction.
Is it a sin to watch Harry Potter?
... sometimes ...
If you are struggling with witchcraft/wizardry, or your conscience tells you you should not be watching it, then it is sin.
If you are not struggling with witchcraft/wizardry, and your conscience is clear while watching, then it is not sin.
Some will say that God's absolute truth is being ignored by this, but saying that "absolute truth defines all sin" ignores all of the Pauline epistles. There is truth, and absolute truth, and God's Holiness is absolute, but: the Christian is guided by the Holy Spirit, and the Holy Spirit speaks to us through the conscience. For the Christian, sin is denying the conscience.
The worst thing about these movies, as any movie, is that: they are distracting us from doing good for others. If we are entertaining ourselves, we are neglecting our calling. < we are called to bear good fruit.
If you have ever judged others for watching Harry Potter, ever in your life, IT IS A SIN FOR YOU TO WATCH IT!
^this goes for anything that you've judged someone for.