"Another dangerous source is books."
So? Burn them. Isn't that what you people do?
"Especially such works as Harry Potter."
Harry potter is out of fashion. You should be bitching about Twilight. Do try to keep up.
"Do you know that the names and spells in those stories are real?"
Someone's never had a Latin class if they think that the names of those spells are real.
"I started reading one of those books,"
Heathen! Heretic! Sinner!
"I knew it was wrong and tried to rationalize the content by saying "it's just a struggle between good an evil". Eventually I gave up and treated the book for what it really was, witchcraft."
The second you can use any Harry Potter book, or combination of Harry Potter books, to cast a spell I'll believe you. Let me know when you can make something levitate by uttering some pseudolatin and waving a stick around.