The whole thing being illustrated there is that they were willing to die for the rule of law. They were not treating this as a shootout between two opposing armies, but as the rightful authorities re-imposing order. It was not the greatest tactical approach, but it was definitely one of moral superiority. And they won, and at the end, you see them standing over a line of shackled prisoners, rather than a mound of corpses. That is consistent with the previous movies, such as Batman saving the Joker from falling.