The Ally is eminently watchable, although it seems like it shouldn’t be. Unless, that is, you go to the theater to be lectured on geopolitical issues. Itamar Moses’ new drama runs more than 2½ hours, and you might feel like you spend about two hours of it watching one character, who’s speaking to another person on stage, deliver a speech that elucidates a stance on the Israel-Palestine conflict, complete with historical references, geographical context, statistics and preemptive rebuttals.