Maybe it's not a problem with explaining the concept per se, it's just that its consequences are unpleasant. Feels like you are telling people that heroic responsibility is one of the possible choices, a one that they didn't make, but could have made, and perhaps even should have made. -- There probably are good reasons why most people don't take heroic responsibility, but these are difficult to explain. So it's easier to pretend that the whole concept does not make sense to you.

Also, it's not my responsibility to understand the concept of heroic responsibility. :D

EDIT: It may be related to the status-regulation emotion that apparently some people feel very strongly, and some people don't even know. The problem with "heroic responsibility" might simply be the emotional reaction of: "Who do you think you are that you even consider taking more responsibility than other people around you?! That is a task worth of a king; and you obviously aren't one. And you try to explain it to me, but I am also not a king; I don't even pretend to be, so... this whole stuff doesn't make any sense. You must be insane."