Must? Not sure. Art can challenge you without "seducing" you "into conniving in the violation, because we have permitted our fantasies to accept what we know to be revolting".
By avoiding challenge you flee from Truth.
Life's filled with enough challenges, and one simply cannot avoid Truth indefinitely. Further, one needn't elevate the process of tempting or being tempted to "art" in order to be properly challenged or to encounter the truth.
‘Paradise Lost’ also tempts the reader to sympathize with Satan - who is a very charismatic character.
You continue it deliberately not understand that sentence. It’s a divided sentence, working with the barrier between what you might fantasize about and what you would actually do. If you can’t acknowledge that you would (and probably occasionally do) fantasize about things you know are wrong you can’t understand Truth. It’s in the nature of sin that we want to do things we know are wrong, and in being righteous we don’t do them. Have you never thought the world would be a better place is Person X died? But you don’t kill them, and you probably even post-pend that thought with a bit of guilt because good people know you really shouldn’t wish ill upon others. That’s the exact same thing, your fantasies have accepted something (”sure would be nice if that jerk had a heart attack”) that you know is revolting (wishing people dead is wrong).
The fact that you continue to grossly not understand that sentence shows exactly what I’m talking about. You are fleeing from Truth, you will not acknowledge that we do dream of things we shouldn’t. Lolita isn’t tempting, the actions in the book always remain wrong and the reader never doubts it, it’s simply reminding us of the dream-action barrier.