Now, hear me out. If I'm going to spend money somewhere, I'd like to know that the company I'm spending it with is acting in a way that I find ethical. In fact, I'd like to hold them to a higher standard, since it's so much easier for companies to have moral failings than it is people.
> Censorship is suppression of speech or other communication which may be considered objectionable, harmful, sensitive, or inconvenient to the general body of people as determined by a government, media outlet, or other controlling body. - Wikipedia
Amazon is acting as a censor. Now, it's not illegal. But I do find it to be distasteful. So I'd rather not support them. This article is one of a few lately that lets me know that Amazon and I are apparently looking at the world in a different way, and so I shouldn't patronize them anymore.
Finally, it's incredibly important to hold these companies to a higher standard as they grow larger, because they become more and more influential. Most of my local bookstores have closed, and while there are other places to buy books online, I don't have the same relationship with them as I once did with Amazon. Now I'm in the process of checking out alternatives, but still: Amazon has become synonymous with "buying a book on the Internet."