And, if what you're saying is universally true for kids, or even nearly so, then I'd say that we (collectively, as adults) have failed them in strolling hand-in-hand with them into a world wherein personal relationships are not viable without a profiteering third-party intermediary.
It's a bit extreme of a position.
And, I think it's reasonable to question how close his friendships are if they are dependent on Facebook.
But, that's probably true of society in general, wherein we seem to be trading quantity for quality where personal relationships are concerned. And the generation coming up now has almost no reference point as to any other way.
He didn't join Facebook because he was losing friends, he joined Facebook because of the social friction NOT being on Facebook caused. This is both less coercive and more insidious.
If you just ... stop ... you may find your social circle leaving you behind.