They're conceptually related to reporting exploits in public. We report exploits in public because we operate under the assumption that if the "good guys" have figured out an attack vector, the "bad guys" have too.

We honeypot criminals-in-the-making under the assumption that if the "good guys" can get the person to prepare for violence resulting in death, the "bad guys" can too. Whether the honeypot is too sweet or unreasonably sticky is an excellent matter for discussion in a court of law (but it's probably worth noting, as a pulse check, that more than 99.9% of the population isn't even in the market for C-4 of any kind, let alone for terroristic ends).