I think there’s a misconception that the SE’s are arbiters of moral standards. They aren’t. They’re in a business, and their stated objective is to deliver the most relevant results to any given search. Accordingly, they’ve published broad sets of guidelines in an effort to persuade webmasters to conform to certain protocols. These protocols are not, and never will be moral edicts.
In the competition for traffic, some will largely adhere to the guidelines, and some will not. Having hung out with some of the best SEO’s in the business for many years, I know many that are both white and black hatters. They’re simply hedging their bets. Moreover, you only see these issues raised in the more competitive commercial areas like gambling, online pharmacies, adult and the like. How many black hatters come from the quantum physics discipline?
That said, I agree that theft of content violates any moral standard. But manipulation through link exchanges, buying links, etc., for instance – what universal moral principal is violated? I guess it’s a matter of opinion, and the degree to which you think you’re being hurt.