That task was surely harder than thinking of the technique. Or perhaps they are talking about the time it took designing, writing, testing, and perfecting the scripts and the web pages to handle one-click shopping. That was surely a substantial job. The issue here is the general idea, and whether Amazon should have a monopoly on that idea. That is the question.
Public disgust can affect their profits.
People have pointed out that the problem of software patents is much bigger than Amazon, that other companies might have acted just the same, and that boycotting Amazon won't directly change patent law. Of course, these are all true. If we mount the boycott strongly and lastingly, Amazon may eventually make a concession to end it. And even if they do not, the next company which has an outrageous software patent and considers suing someone will realize there can be a price to pay. They may have second thoughts.