Joker's darkness isn't summoned by Batman's light
I would ask: What light? A child playing in the sandbox, an artist lost in his painting or a girl on the subway enjoying a great song on her mp3, people in love, a walk in nature...that's light. Batman may have "good intentions" and he may care about people but he is very far from the light.
He even says: "Bats frighten me. It’s time my enemies share my dread."
I don't consider him as the incarnation of light in this story.
I do believe, in the context of this story, it was he that attracted Joker to Gotham.