Data could be (and often has been) totally scientifically legit if participants are mistreated or exploited! Take the hypothesis: "I bet human beings will develop strange psychological effects if they have zero human contact before turning 4 years old." We could test that, and come up with legit results, by putting babies in weird cages, etc, but we don't because it would be unethical.
Says wikipedia about the experiments Nazis performed on their prisoners:
Contemporary knowledge concerning the manner in which the human body reacts to freezing is based almost exclusively on these Nazi experiments. This, together with the recent use of data from Nazi research into the effects of phosgene gas, has proven controversial and presents an ethical dilemma for modern physicians who do not agree with the methods used to obtain this data.[19]
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Says wikipedia about the experiments Nazis performed on their prisoners:
Contemporary knowledge concerning the manner in which the human body reacts to freezing is based almost exclusively on these Nazi experiments. This, together with the recent use of data from Nazi research into the effects of phosgene gas, has proven controversial and presents an ethical dilemma for modern physicians who do not agree with the methods used to obtain this data.[19]
http://thetrichordist.wordpress.com/2012/06/18/letter-to-emily-white-at-npr-all-songs-considered/