Google, as a search engine, is a generic "find the most relevant thing based on the keywords I provide". Amazon, as a search engine, is closer to "find the things I would be most likely to buy based on the keywords I provide". The two functions are entirely different.
I didn't make any comment about it being "less evil" (was that intended to be a quote?); I was making a comment about the intended function of the service. I could have substituted in DDG or Yahoo! or Bing and the point would be the same; equally, it makes as much sense to provide Amazon-based results to me as it would do to provide results from Target or Walmart.