The term is pejorative. "Quote miners" are often accused of contextomy and misquotation, in an attempt to represent the views of the person being quoted inaccurately. For example, if a person being quoted disagrees with some position, a quote miner will present quotes that suggest that instead, this person is supportive of this position. Material that ostensibly bolsters this position is often taken out of context. Exposition that is at odds with the argument being made in the same text is excluded or otherwise obscured.
The expression is also sometimes used in a slightly weaker sense, merely meaning that a quote is being used to support an idea that the original author rejects. In this second case, even a quote which is accurate can be considered a "mined quote".
The above quote itself could be turned into an example of quote mining:
MOreover, quote mining is a favorite work of anti-Islamic writers, usually as they quote out of context and jumps from ayah to another ayah having no relevance to prove their allegations against the Quran and as a whole, Islam. Common examples are Ayaan Hirsha Ali, Taslima Nasrin, Aaron Shohri, etc.
This quote is clearly taken out of context because Darwin continues:
In this case, the originally quoted sentence is a rhetorical device: Darwin is first admitting to the 'seeming' strength of a criticism in order to better refute it. Darwin, in fact, goes on to devote three further pages to this subject, all of arguing as to why he believes the original objection to be unwarranted. Thus, presenting the original sentence alone gives the reader a false impression of what Darwin thinks about the subject: that he thinks a problem is unsolvable, when in fact in context he was merely admitting that it might seem unsolvable, at first. The creationist organization "Answers in Genesis" has noted the unfairness of quoting Darwin in this way, and urged others not to use the quote without including the following explanatory material.
Stein stops there, then names Darwin as the author in a way that suggests that Darwin provided a rationale for the activities of the Nazis. However, the original source shows that Stein has significantly changed the text and meaning of the paragraph, by leaving out whole and partial sentences without indicating that he had done so. The original paragraph (page 168) (words that Stein omitted shown in bold) and the very next sentences in the book state:
According to John Moore writing in the National Post:
The Expelled Exposed website also points out that the same misleading selective quotation from this passage was used by anti-evolutionist William Jennings Bryan in the 1925 Scopes Trial, but the full passage makes it clear that Darwin was not advocating eugenics. The eugenics movement relied on simplistic and faulty assumptions about heredity, and by the 1920s evolutionary biologists were criticizing eugenics. Clarence Darrow, who defended the teaching of human evolution in the Scopes trial, wrote a scathing repudiation of eugenics.