Facebook Helped the FBI Hack a Child Predator

Good, they should do it more often.

If the technology exists to put people known to be terrorizing people, and hurting people online behind bars then we should absolutely be doing it.

"people known to be terrorizing people"

Just sit and think about how these words could be tortured.

At what point do a prosecutor, judge, and jury get to weigh in on "known to be" in your world?

I'm sure that 'child predator' is not an annoying civil rights activist.

TL;DR:

Facebook saw they had issues with a child predator who used Tor via Tails, so the FBI tried to hack him, but their de-anonymization failed on Tails. Facebook gets more concerned and commissions an 0day (for $$$$) and hands it to the FBI to do the work the FBI should have done.

FB has no guarantee that the FBI didn't keep using the exploit for the last 3 years for any other purpose.