Sin is not ‘fulfilling’. Two old aphorisms come to mind:
“God must have really hated me, He gave me everything I wanted.”
and
“You can never get enough of what you really don’t want.”
Why not? If a person has the evil desire to look at nekked girls, then he "fulfills" that evil desire by hitting a few buttons on the keyboard. But in hell, there won't be an opportunity to do that, yet he might still have that evil desire. At least, this is what I thought MLG was talking about.