Finally watched Obsession.

This answer regarding Black Magic from the FAQ of The Green Man Shoppe & Apothecary seems to sum up the horror the film portrays:

*To do magical or spiritual work to bend the will of another person to our own is to seek to negate that freedom...If love is what you wanted, if your spell works, what you will get is slavery. If you don’t see the problem with that, then at least consider the consequences for yourself. What you enslave you are enslaved to.*