I found an article on the Atlantic that provides additional context to Chris Hayes's remarks and it also asks a series of followup questions about whether people should be called heroes under different circumstances.

Link here.

The followup questions seemed to be worth reposting in their entirety:

1) Are all American war dead heroic because, if nothing else, they had the courage to volunteer for service knowing they might ultimately give their life for their country? That seems heroic to me. But if they're all heroes, does it follow that everyone in the military is a hero? Why is dying necessary? And if everyone who volunteers is a hero, what about the guys who would go AWOL if sent to fight, or who assault their commanding officer, or who run away in combat? What about the ones who are dishonorably discharged? Was Bradley Manning a hero? Had Lynndie England died in Iraq, would she have been a hero?

2) What about people who volunteer for foreign armed forces? Are they all heroic? Or does it depend upon their country? If an American helping to liberate Libya would've been a hero had he died in action, shouldn't the Germans from NATO engaged in the same conflict be heroes too? What about the Islamic fundamentalists fighting alongside NATO? Heroes?

3) What about the morality of the cause? Does anyone think brave Nazi soldiers during the World War II era were heroes? How about the soldiers in Stalin's army? Does the nature of the mission matter, so that a Soviet soldier who died liberating a death camp was a hero, whereas another who died while ravaging German civilians he was ordered to take revenge upon isn't? There's this reality to confront: if bestowing the title hero has nothing to do with the rightness or wrongness of the cause or mission, we'll have to grant the honorific to individuals who took part in deeply immoral acts... and yet, if the mission does matter, do we really want to deny the heroism of a GI who jumped on a grenade to save his platoon, even if we think the platoon's presence in country X was immoral? It's a confounding choice.

4) Speaking of jumping on grenades, isn't "hero" often invoked in common parlance as if it means even more than serving and dying? For example, when we hear someone described as "a World War II hero," don't we expect that he did more than fall overboard and drown en route to the D-Day invasion? Don't we assume from that adjective that he undertook some dangerous mission, or distinguished himself in combat, like the younger Bailey brother in It's a Wonderful Life? Were the average American to watch From Here to Eternity, would he or she call Robert E. Lee Prewitt a hero?

5) And say, for the sake of argument, that all American war dead are heroes, strictly defined, but that the word and its emotional resonance is being manipulated by advocates of an imprudent war. Is it better to give soldiers an honorific they deserve, consequences be damned, or to withhold an honorific they deserve to prevent future soldiers from needlessly dying?