And if they didn't the headline would read: "Facebook fails to stop malicious and illegal content from being shared on their Network! Should they be shut down?!"
If we'd be talking really malicious stuff like chid pornography then in the context of filesharing these companies already have systems in place to distinguish content, so blanket banning of torrent files seems blatantly unnecessary.
This is the real strawman, as nobody on this entire thread is talking about illegal music. On the other hand, there's a strong and persistent thread of calls for tech platforms like Facebook to control "malicious or illegal" information being spread on their platforms: an obvious example is the NZ shooter's manifesto + video.