Whether Amazon is in the right or in the wrong depends on their endgame.

I am sure I don't understand.

Amazon, like most businesses and individuals, is taking actions today that it hopes will lead to advantageous outcomes. You are saying that the moral value of these actions does not depend on what the actions are, nor how the actions affect others, but on what ultimate outcome Amazon hopes to achieve (whether they achieve it or not?).

offering the lowest prices to consumers because then can

"Because they can"? Surely they are offering low prices as part of a business strategy. Jeff Bezos doesn't care about anybody's dipaers.

What exactly is the harm that you hope to avoid? One single entity somehow controlling the world's supply of diapers? Aren't there obvious workarounds in that unlikely scenario? (And it strikes me as odd that you aim to preserve competition by using an entity which has undisputed monopoly power over using force to regulate business.)

When Amazon took on Quidsi, everybody benefitted. Now the "victim" that you seem interested in protecting is launching a substantially bigger effort to serve customers. Would this had happened if you had protected Quidsi from Amazon's clutches?