Because that is what warlocks are, if we want to cure them we agree they are mentally ill. The compulsion to break laws even if it is not in their best interest can be seen as a mental illness.
I don't agree to that at all. We are talking about supernatural energies warping their mind. Difficult to apply human psychology when the supernatural is involved.
"The Blackstaff is what keeps that kind of thing from driving him insane and turning him into a giggling villain. Yah you don’t go messing with black magic in the Dresden Files, it’s very very bad for you. " - Jim
"Use of black magic warps your mind" - Jim
I will admit though, that Jim has left it up for debate on purpose.
"As for violating the laws of magic themselves turning you good or evil, well.
There’s something to be said on either side of the argument, in the strictest sense, though one side of the argument is definitely less incorrect than the other. But it’s going to take me several more books to lay it out, so there’s no sense in ruining the fun.
"