Asserting not(x) to focus the topic on x

I recently rediscovered a great short story I enjoyed in my youth, Love is a Fallacy. I never did study logic formally, other than in the computer science sense. But that didn't really address things like the emotional appeal of Ad Misericordiam; it really doesn't come up when programming.

It did get me thinking about an interesting argument technique: asserting not(x) to focus the topic on x, elevating an otherwise non-issue as something contentious and open for debate. As an example:

My opponent is not a child molester. He is not the type of person who would blatantly rob children of their innocence for his own perverted sexual gratification. Why would anyone associate him with pedophiles like Father Brendan Smyth?

And so on. Does anyone out there know a formal name for this technique, or examples of where it has been used? Let me know in the comments.