Some quick observations about the mid-20th-Century use of 'scientism':
- It was used in a more overtly political way by both religious and non-religious authors who tended towards the right end of the political spectrum.
- The term was generally used to brand its target as a Faustian, secular religion, implying that adherents of the targeted view, though they pretended to superior rationality, had in fact made their own leap of faith.
- The destination of this leap of faith was in the first instance a 'liberal' ideology, in which a Whiggish belief in progress and an overly rosy view of human nature figured prominently. (This aspect of the term's function fades in the libertarian uses.)
- The phrase was rhetorically convenient for right-wing authors, since it assimilated secular liberalism with Marxism (a more obvious secular religion that was optimistic about history and human nature and that made a great show of being a purely rational science).
Some of the quoted passages seem haunted by a fear of Marxist communism, which is more pronounced in the passage by Polanyi ('soul-destroying tyrrany'). The fear also comes through as a concern about loss of freedom (esp. in the passages from Lewis and Polanyi), with the suggestion in Hayek's 1942 statement that there's something 'slavish' about scientism.
It's interesting to see how the French 'scientisme', originally directed against Saint-Simon and Comte (who really did envision secular institutions that mimicked religion), morphed into the English 'scientism', which was used just before and during the Cold War as an epithet for a broader array of secular views.
My sense is that today, 'scientism' has largely shed its overtly political connotations and is more often used simply to imply that someone has illegitimately applied phsyical-scientific method beyond its proper domain.