My bet is that there are as many molesters in your local mall as at WDW on a per capita basis every day. A child is most likely to be molested by a relative or family friend, not a stranger.
WDW has plenty of security, both uniformed and plain clothes. But you as a parent must take the responsibility of safeguarding your kids. Don't do things like letting them go to the pool alone, letting them play in the game rooms alone, and letting them roam around alone. Make sure that they understand how a molester works--offering candy or asking for help looking for a puppy.
Unfortunately, too many parents check their brain at the door when they go on vacation. Use some common sense, and make sure your kids know how to use theirs, and you'll be perfectly safe.
Anne