I was also heavily influenced by Schaeffer when I read him as a teenager in the '70s. I agree he lost his way, but the social-political path was the direction he was headed from the start. He was influenced by Abraham Kuyper, the Dutch Reformed theologian and politician. Kuyper’s thought laid the groundwork for the original “culture war” of fundamentalism vs. modernism in the 1920s. Being a good Calvinist, Kuyper took the idea of “total depravity” to its limit, as did his disciple Cornelius van Til, by arguing that just as there are two types of men – the regenerate and the unregenerate – there were two types of science. As David Naugle characterized Kuyper’s view of science in his book about worldview:
“There is not a neutral, scientific rationality leading to certain objective and shared conclusions. Instead, scientific theories are a function of the religious backgrounds and philosophical orientations of the scientists or theorists. For these reasons, disparate worldviews, Christian and otherwise, are at the heart of science broadly conceived.”
Kuyper’s influence on the current Culture War/Intelligent Design argument about the “atheistic presuppositions” of science shouldn’t be too hard to recognize. Schaeffer picked up these ideas from Kuyper and van Til and popularized them (again) in the '60s and '70s, and here we are.
The problem with both Kuyper and Schaeffer, in my opinion, is that their analyses of culture are superficial. “Culture” involves a lot more than just philosophy, which they failed to recognize.
Edit: I wanted to highlight the notion that “objective and shared conclusions” – otherwise known as “facts,” or the knowledge base that we must share – are negated in Kuyper’s system. This, again, is the root of what we are seeing right now in the arguments about “fake news” and “alternative facts.”