Don't rely on Wikipedia as being a proof source for anything. Most of the articles are well written, but it is a wiki, which means that there is a lot of opinion mixed with the content. No one proofs it for accuracy.
From my perspective, ethical SEO practices are more an issue of deceiving customers into thinking they are going to see a particular result, but something very different is delivered, such as guaranteed traffic, guaranteed first page results, submission to 750,000 search engines (yes, there used to be an ad that claimed this), etc.
I don't think of keyword stuffing as being unethical. It is a form of spamming the search engines and it is foolish.
Websters: Ethics - the discipline dealing with what is good and bad with moral duty and obligation.