A blog post by Alistair Roberts, as curated by Steve Sailer. (Steve's version is shorter and more targeted; the original blog post is the fourth in a series on triggering and suffers for its reliance on the particular issue.)
It seems like a very useful dichotomy, and strongly reminds me of Ask and Guess.
I believe that part of what caused the rise of sensitivity-based discourse is that some people got tired of discourse that seemed to have a premise of "let's calmly consider the plausible claim that the interests of people like you are dispensable", and lost points for showing anger. (Other motives include quite ordinary power-seeking.)
As an explanation for a society-wide shift in discourse that seems quite implausible. If such a change has actually happened the cause would most likely be some broad cultural or sociological change that took place within the same time frame.