I don't know. They may be because he's an American. Typically I'd think this would have been swept under the carpet, but being caught on camera hitting a boy with the wrong passport could cost them.
Mentioning the American passport, any idea how your legal system would treat a minor who goes overseas and throws Molotov cocktails at security forces?
I'd imagine the visceral brutality of three grown men beating the hell out of a skinny teenage kid will trump anything the kid may have allegedly done, and any attempts to blame the kid for what happened to him will cast the Israeli government in an unflattering light. The international public may also be inclined to wonder how often this sort of thing goes on when the cameras aren't rolling.