As realistic as trickle down economics

Right, because realism was clearly McTiernan's priority when he filmed this.

It's more a case of a cop, rather inexplicably trained in asymmetrical warfare, beating persons ostensibly trained in asymmetrical warfare by turning their own tactics against them. We are to suppose that the training came from experience gained from a war in which the Americans lost, mostly because they couldn't grasp the essentials of asymmetrical warfare. Split hairs if you must, but the verdict of history and about a half a billion viewers suggests this was sufficient for suspension of disbelief. That said, persons actively looking for realism in this film franchise should probably join a pack of noseblind warthogs searching for truffles in the woods. Who knows? There might be something out there about trickle-down economics. Cheers.