I am no fan of it, but why do you think it is destructive?
Because Facebook periodically resets its user's personal settings, exposing you and your info to the world.
Personally, I feel Facebook is evil. That's my opinion, your mileage may vary.
I’m not the individual who said that FB was destructive, but from a law enforcement point-of-view, Facebook is a great tool for criminals.
People accept friend, who they may know noting about, and then share all kinds of intimate details such as work schedules, vacations, and so on. Now, the guy who wants to rob your house knows that you just bought a new flat-screen TV or computer and that you’ll be at work from 8 -4 and the dog is at the vet getting fixed.
FB can also be used for cyberstalking, corporate espionage, child luring and exploitation and so on.
Not just FB, like everything else, all of the features for the average user are also features that can be used by the bad guys. And people tend to put way, way too much personal information out on the Internet.