I agree whole heartedly about the first sentence. I disagree, however, with the absolute nature of the second point. Rather, with normal people, identifying 'jail bait" does not lead to murder.
Some criminals, however, don't operate in the normal world and don't consider things objectively. Thus, identifying "jail bait" could lead to some having feelings of betrayal, awaken dark fantasies about "solving problems" in what they perceive to be "major league" criminal style, or simply exacerbating an existing tendency towards violence etc.
A good example of this is the Virginia Tech case where a 19 year old student is accused of murdering a minor after a brief relationship that might of been sexual. If she threatened to turn him in, he had many legal options (semi affluent family and ability to get a good lawyer, clean record, minor had lied about her age etc.).
Instead, he apparently murders her with assistance from another student whose dark fantasies about serial killing had been awakened by the incident.