What makes apostasy different from any other sin is the lack of remorse. Even most child molestors probably believe that what they have done is wrong; but they just couldn't help themselves. Sex, after all, is the most powerful human instinct. In most people it overrides not only ethics and reason, but even self-preservation! So when a child-molestor is caught, he is likely to recognize that he was wrong and repent.
Contrast that with apostasy. Unlike sex, apostasy isn't some passion that overwhelms a basically good person and makes them do bad things. Apostasy is a very conscious, willful decision that involves the most human part of us: our intellect. Unlike the child molestor, the apostate isn't going to be contrite if he or she is caught. Chances are, the apostate won't even deny the accussation and will proudly defend their decision.
So even though the child-molestor has caused a lot of suffering and the apostate none at all, I totally understand why the former is handled with kid gloves while the latter is dealt with so harshly. Child molestors are just weak people who gave in to their basest instincts. Apostates, by contrast, are usually very strong, spiritual people who deliberately turn against Jehovah and his organization. It's the difference between Eve's sin and the fall of Lucifer. Eve and her husband were forgiven for their weakness, but Satan will never get that because he will never repent.