What do you mean “Let it slide”? He repeatedly pressed the guy on the point. He cut the spokesman off when he tried to change the subject. He stayed on the point about Isreal bombing innocents for as long as he reasonably could, and refused to accept any of the evasive and weasely answers the spokesman tried to give him.
What exactly do you want here? For him to scream at the guy, call him a murderer, tell him he’s going to burn in hell? That’s not journalism, that’s self-indulgence. Wolf was doing exactly what a good journalist should do, trying to get to the truth of the story, and he only gave up when he’d gotten as far as he could from this particular avenue.