His argument reminds me a lot of the ones used by enablers -- enablers of abusers, drug addicts, alcoholics, you name it: That is, "they" won't change until "they" want to. We can't make it happen. And so the best we can do is get out. Then, "they'll" hit bottom and come to their senses.
Such an approach might well make sense in cases of private behavior -- thankfully, I don't have enough experience to know one way or another. But when it comes to very public behavior -- behavior that can result in a suitcase nuke going off in a major American city -- the reasoning is defective.
Friedman's approach might have worked in a different age, one without cell phones, computers and -- oh, yeah! -- suitase nukes. But if we fall for Friedman's line that a "stronger America" will result from abandoning Afghanistan, and then just leave, what could happen as a result? After all, it's important to weigh the risks of a proposed strategy, not just consider possible positive outcomes (as critics like Friedman would have been the first to tell the Bush administration).
Will America really be "stronger" -- as Friedman argues -- if Afghanistan falls to Al Qaeda and its allies, who then push the fight into the already-unstable nuclear power of Pakistan?