I'm not sure what you mean.

If you mean what I think you mean, I'm ignoring it because I'm going with worst case. Rather than tracking how the probability of someone making the threat reduces slower than the probability of them carrying it out (which means a lower probability of them carrying it out), I'm showing that even if we assume that the probability is one, it's not enough to discount the threat.

P(Person is capable of carrying out the threat) is high enough for you to pay it off on its own. The only way for P(Person is capable of carrying out the threat | Person makes the threat) to be small enough to ignore is if P(Person makes the threat) > 1.