This is obviously not the case, otherwise how is anybody detecting the crimes in order to accuse Facebook of them? If someone is running an ad to sell drugs or

This is obviously not the case, otherwise how is anybody detecting the crimes in order to accuse Facebook of them? If someone is running an ad to sell drugs or violate some other law, the users will see the ad and can report it to law enforcement. Law enforcement then investigates to find out who placed the ad and goes to arrest them.