Thanks to a very rational comment somewhere I learned a new term this morning - The Overton Window.
Found it at Wikipedia.
The Overton window is a concept in political theory, named after its originator, Joe Overton, former vice president of the Mackinac Center for Public Policy. It describes a "window" in the range of public reactions to ideas in public discourse, in a spectrum of all possible options on an issue. Overton described a method for moving that window, thereby including previously excluded ideas, while excluding previously acceptable ideas. The technique relies on people promoting ideas even less acceptable than the previous "outer fringe" ideas. That makes those old fringe ideas look less extreme, and thereby acceptable. The idea is that priming the public with fringe ideas intended to be and remain unacceptable, will make the real target ideas seem more acceptable by comparison.
The degrees of acceptance of public ideas can be described roughly as:
The Overton Window is a means of visualizing which ideas define that range of acceptance by where they fall in it, and adding new ideas that can push the old ideas towards acceptance merely by making the limits more extreme.
My biggest problem is spending too much time and energy at the unthinkable end of the continuum.