About two hours into "Gladiator II," Hanno steps up to deliver a speech that might finally tell us why we should care about anyone or anything in Ridley Scott's newest sharks-and-sandals potboiler. Fred Hechinger plays Emperor Caracalla in "Gladiator II" Ironically enough, the real-life Caracalla, described as a soldier's emperor who bore all the hardships of an enlisted legionary, might …