Pardon? Facebook IS evil for allowing this content.
Facebook doesn’t, can’t actually, supervise everything that goes on in their system.
I’m sure they close such sites when they’re brought to their attention, but the perps will just open them up somewhere else.
That’s the unfortunate side effect of an uncensored medium, lots of bad things as well as good things show up in it.
Once had some disgustingly graphic child porn images sent to me by email from Netherlands. Don’t know why they chose me or how they got my address. Immediately contacted local cops and FBI. Figured it was the best way to protect myself in case those images downloaded themselves.