Neither Hermione nor Harry dispute that they have a responsibility to protect the victims of bullying. There may be people who would have denied that, but none of them are involved in the conversation. What they are arguing over is what their responsibility requires of them, not the existence of a responsibility. In other words, they are arguing over what to do.

Human beings are not perfect Bayesian calculators. When you present a human being with criteria for success, they do not proceed to optimize perfectly over the universe of all possible strategies. The task "write a poem" is less constrained than the task "write an Elizabethan sonnet", and in all likelihood the best poem is not an Elizabethan sonnet, but that doesn't mean that you will get a better poem out of a sixth-grader by asking for any poem than by giving them something to work with. The passage from Zen and the Art of Motorcycle Maintenance Eliezer Yudkowsy quoted back during the Overcoming Bias days, "Original Seeing", gave an example of this: the student couldn't think of anything to say in a five-hundred word essay about the United States, Bozeman, or the main street of Bozeman, but produced a five-thousand word essay about the front facade of the Opera House. Therefore, when I evaluate "heroic responsibility", I do not evaluate it as a proposition which is either true or false, but as a meme which either produces superior or inferior results - I judge it by instrumental, not epistemic, standards.

Looking at the example in the fanfic and the example in the OP, as a means to inspire superior strategic behavior, it sucks. It tells people to work harder, not smarter. It tells people to fix things, but it doesn't tell them how to fix things - and if you tell a human being (as opposed to a perfect Bayesian calculator) to fix something, it sounds like you're telling them to fix it themselves because that is what it sounds like from a literary perspective. "You've got to get the job done no matter what" is not what the hero says when they want people to vote in the next school board election - it's what the hero says when they want people to run for the school board in the next election, or to protest for fifteen days straight outside the meeting place of the school board to pressure them into changing their behavior, or something else on that level of commitment. And if you want people to make optimal decisions, you need to give them better guidance than that to allocating their resources.