Theory: People hear murder, and think, "Oh, the best you'll do is get them a couple years off, no judge will let a murderer go free." But when someone hears "molesting a child", they think, "They're probably guilty regardless of what you think, but you have a chance of convincing a jury and then unleash this monster on us."

Of course, this is working on a subconscious level.

I suppose the theory you're supposed to think of is "molestation is more graphic than murder"? That can be tested by substituting another, more graphic word for murder, e.g. "shot, exploded, cut up". (Trying not to get too graphic here.)