You'd have to be high as a kite to believe Harry Potter is witch-craft.
It's a movie, originally scripted on a napkin by a then-homeless British woman.
It's comparable to Mother Goose's Stories, Arabian Nights, and most of Disney animated movies.
If your child takes Harry Potter too seriously, and speaks pig-Latin while waving a plastic wand, simply send him/her to Switzerland for a year.
As for magic cards...
... people still play with those things?!?!?
Dungeons & Dragons, now there's a classic!