I think too critically virtually all the time to not think deeper about this.
Who frightens you more:
1. A convicted sex offender who served his time for his horrible abuse of children, but has been out of prison for a decade or more and knows he is being constantly watched because everyone knows who he is.
OR
2. An unknown person who, during the Purge, kills sex offenders because this unknown person knows they can kill and get away with it during the Purge.
On the one hand, you have a horrible person who has been proven to do horrible things, but has been punished and is being watched all the time so probably cannot commit further crimes against children... on the other hand, someone perhaps that you even know really really wants to kill someone and waits until they know they can get away with it.
Honestly, if I live in that world... I'm going to be increasingly less afraid of that sex offender I know where he lives and know a lot of people are watching him... but I don't know who the maniac is that takes advantage of the Purge to kill people. Sure, maybe this time he killed a sex offender, but do you KNOW for sure that wasn't about convenience? And he has a taste for killing now, so likely to kill again... and maybe he has a sliding scale so today it's sex offenders, tomorrow its someone who looked at him funny.