Despite that he regularly used "evolution" and "the theory of evolution" interchangeably from then on including the wonderful "the searing truth of evolutionary theory"

There's some subtlety I can't get here. "Evolution" obviously isn't identical with any "theory of evolution"- the one is an attempt to explain the other- but in the context of opposing someone who is refusing to accept the obvious existence of either, it's a peccadillo if an offence at all. I'm sure you wouldn't complain about someone who talked about "the searing truth of gravitational theory" to a nutcase who was trying to persuade you to jump from the 16th floor.