Both great discussions as well as I story that enjoyed even I agree with others that protagonists actions are reprehensible at the least. And that airships aren't a particularly sensible travel method, which is why they did die out.
Firstly, it shows that, in a world where people won't stop Hitler because it might not suit them, you pretty much have to invent your own values.
Though I think this is misplaced, no one with any sense would argue there is anything good about Hitlers crimes, but how much different is causing the millions if not billions of lives that currently existed until Hitler was removed from not existing?
Time travel ethics, now this is an interesting area. Consider, if we erased the current population of 7-point-something billion and replaced them with a different population of 7-point-something billion, we have done something wrong, correct? Because human life has, in terms of the universal human concepts that keep society flowing and mentally healthy, intangible values, dignity, individual human freedom, etc.
But how about this: We reshape the current population into a different but equally large and equally healthy and happy population. There was no clear point of destroying one and then creating the other, the creation of the other is what destroyed the forebearer. Have we done anything wrong? Has anything been lost? If the "mass" as it were, of human beings and their quality of life as well factored in remains the same, on what grounds is it morally wrong to replace one crop of individuals with another, equally free crop of individuals? After all, by changing time we are not designing or otherwise removing even in an abstract way free will from the human population. The new timeline's population will be, barring altered events in the timeline, as free and causally determined as the previous population. At no point has the "human mass" been destroyed, only reshaped.
And even if you place some weight of ownership on currently existing people over possible people, that it would be a violation of personal sovereignty to erase existing people, there has to be some sort of pragmatic utilitarian ratio of the cost of freedom vs. increased population and well being. So just exactly how much better does the new timeline need to be for us to be justified in erasing the current crop of humanity? Rationally speaking, if one follows consequentialist rather than deontological ethics, there has to be a certain point of increased human life and well being that outweighs the collective loss of freedom/violation the current population would suffer.
And from a purely utilitarian standpoint, seeing as "erasing" or even "reshaping" are clumsy metaphors that imply a physical coercion that is not there, is any harm being done at all even if the replacement timeline is only just as good and not any better? If the current timeline's population will never have existed and thus will not suffer any pain or displeasure or fear or doubt or sense of violation, isn't it not a crime to change history so they never come into being? Or maybe, even if that doesn't cause any additional pain, maybe unless we are minimizing pain; making the world better, the future better, we can't justify the act. But if we reasonably can, then we can. Right?
Unless one wants to get into the deontological side of things were certain things are always wrong no matter what and classify this as one of them, I suppose the primary ethical limitation on altering the timeline would be that we cannot reasonably claim to have a reliable and responsible power over the changes. Any changes we make to create a better world, no matter how justified that would make our actions, cannot be guaranteed to not create a worst world. That seems to be the most pragmatic argument for an intrinsic unethical quality to altering the timeline; but that doesn't seem to be a quality that couldn't be outweighed. For instance, if the current timeline has a nuclear war and most of humanity dies, isn't it worth risking all humanity having died to try to alter the timeline to prevent that destruction? Maybe, from a pragmatic, humane standpoint.
But then what about the Holocaust? Considering the sheer carnage involved, there has to be a certain threshold of reasonable certainty that could theoretically be achieved through research and running the possible scenarios that would eventually make it the ethical decision to take a calculated risk by changing the timeline.
So the limitation there is not ethical in of itself, but practical: can any available or achievable prediction model reliably allow us to make responsible choices altering the timeline, or is the course of human and other events too unpredictable to allow for ethical and responsible time alteration?
