You don't say a herd of cows ought to be a good sport. A crying baby ought to be a good sport. That tree is being mean, casting shade. The anthill ought to return my sugar.
That is why there is no conflict. Because they are not the same morally and thus not expected to be treated the same.
Expecting Amazon to be a good sport only makes sense after you have decided that mistakes should not be handled differently depending on who benefits and that you are therefore not entitled to keep your amazing deal. Then you can start to appeal to being a good sport, or the benefits for the public perception of Amazon, or whatnot to explain why Amazon should honor the deal. But this also brings up question like why would you not be a good sport in case of a mistake in favour of Amazon? Note that I do not want to imply any answers here, I just want to point out which kinds of questions one might have to consider.
Everything else is attempts to extrapolate from that.
Many things that are punished if an animal does to a human, are accepted by the billions if humans do to animals.
Many times an adult has a responsibilty a child does not.
The Amazon example is one of the latter kind.
Besides morality there are legal systems. As you get more and more kinds of things, it is expedient to represent corporations as legal entities, but often they are held to a higher standard than just random people. Since a corporation can employ many people and machines, to prepare every sale, they are held to a higher standard for transactions, taxes, reporting, quality of product delivered, and so on. They also have deeper pockets and can take the hit.
I don't see any reason why it should be ok for people to knowingly rip Amazon off. There are worse things (by far) that someone can do, but there's no real justification for doing it.
To compare a company's actions to those of a mosquito strikes me as quite silly. Amazon is run by people who make conscious choices and who are responsible for their actions.
I see this all the time on HN.
Companies don't "do things". The managers (and ultimately Bezos as the top manager) are the moral actors here. "Amazon" is just shortcut name for all the people that work there, this set is ever changing.
In that case, it's not a moral violation if they screw you over, but it's not a moral violation if you end them for screwing you over either. The mosquito isn't violating morals when it bites me, but I'd still have no problem eliminating them all from my backyard if i could do it in a reasonable manner. Not many people claim it is immoral for me to swat the mosquito.
I just don't see why that kind of nihilism suddenly becomes more plausible than usual when you're buying something from Amazon.