Shorter Jackson Diehl: You should never try to stop your friend from stealing, because if that friend then kills someone, how can you object without looking like you're just picking on them?
I'm trying to work out which universe Diehl has spent his life wandering around in that could lead him to conclude that the only way to stop major crimes is to make sure you aid or ignore all the lesser ones leading up to it. It's the Kramer vs Kramer approach to foreign relations, basically: "OK, fine, you can do that, but next time we'll really be angry". Because nothing makes someone think twice about taking that next step like being allowed to take all the previous ones unhindered.
This is to say nothing of the implication that if Obama now does condemn Israel for this (which he would naturally do in the most milquetoast manner possible), Diehl will use that as a reason why the US cannot afford to object in twelve months' time when the IDF start using giant mutant lizards to consume the babies of anyone across the world who didn't like Fiddler On The Roof. Because they were already mean once, you see? And whatever $2.5 billion dollars a year gets you, it clearly doesn't give you the right to complain twice.